{"kind": "language", "major": "18", "item": {"slug": "c", "name": "c", "name_zh": "", "category": "\u539f\u751f\u51fd\u6570\u8bed\u8a00", "summary": "\u52a8\u6001\u52a0\u8f7d\u7684 C \u51fd\u6570", "aliases": [], "content_hash": "f0f111c1b1d706bab8752940dc8df953cdcfd004b363e9b0c069746b63d42a55", "versions": {"10": {"facts": [{"label": "\u79cd\u7c7b", "value": "\u539f\u751f\u51fd\u6570\u8bed\u8a00"}, {"label": "\u53ef\u4fe1", "value": "f"}, {"label": "\u6821\u9a8c\u51fd\u6570", "value": "fmgr_c_validator"}], "tables": [], "aliases": [], "catalog": {"oid": "13", "descr": "dynamically-loaded C functions", "lanacl": "_null_", "lanispl": "f", "lanname": "c", "lanowner": "PGUID", "laninline": "0", "lanpltrusted": "f", "lanvalidator": "2247", "lanplcallfoid": "0"}, "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "label": "10.23", "major": "10", "channel": "historical", "revision": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9", "source_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9", "catalog_fingerprint": "691be281b476dde4374d7f805b2bacc2e75bdef40f1e9d3d42e91f97fe95cfd0"}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "label": "Matching PostgreSQL source archive", "sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, {"url": "https://pg.center/docs/10/xfunc-c.html", "path": "xfunc-c.html", "label": "PostgreSQL 10 English manual", "sha256": "038a55caa67446d85698e7834d7f6bc9499f45b994f586e77faa8d5f607cb813", "language": "en", "original_url": "/docs/10/xfunc-c.html"}], "sections": [], "signature": "", "attributes": {"kind": "Native function language", "handler": "", "trusted": "f", "validator": "fmgr_c_validator"}, "description": ["\u52a8\u6001\u52a0\u8f7d\u7684 C \u51fd\u6570"], "manual_html": "
\n
\n
\n
\n

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\n
\n

37.9.\u00a0C \u8bed\u8a00\u51fd\u6570

\n
\n
\n

\n
\n
\n
\n

\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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37.9.1. \u52a8\u6001\u8f7d\u5165

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\n
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\n

\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u901a\u8fc7\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a037.9.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u52a0\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u88c5\u5165\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u672f\u5757\u201d\u3002\u8fd9\u6837\uff0c\u670d\u52a1\u5668\u80fd\u591f\u53d1\u73b0\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u4e3a\u53e6\u4e00\u4e2a PostgreSQL \u5927\u7248\u672c\u7f16\u8bd1\u7684\u3002\u4ece PostgreSQL 8.2 \u5f00\u59cb\uff0c\u9b54\u672f\u5757\u662f\u5fc5\u9700\u7684\u3002\u8981\u52a0\u5165\u9b54\u672f\u5757\uff0c\u5e94\u5728\u6a21\u5757\u7684\u4e00\u4e2a\u4e14\u4ec5\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff0c\u5305\u542b fmgr.h \u5934\u6587\u4ef6\u540e\u5199\u5165\u4ee5\u4e0b\u5185\u5bb9\uff1a

\n
#ifdef PG_MODULE_MAGIC\nPG_MODULE_MAGIC;\n#endif\n
\n

\u53ef\u4ee5\u7701\u7565 #ifdef \u68c0\u67e5\uff0c\u5982\u679c\u4ee3\u7801\u4e0d\u9700\u8981\u9488\u5bf9 8.2 \u4e4b\u524d\u7684 PostgreSQL \u7248\u672c\u7f16\u8bd1\u7684\u8bdd\u3002

\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u9009\u62e9\u5305\u542b\u521d\u59cb\u5316\u548c\u7ec8\u7ed3\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u88c5\u8f7d\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_fini \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u5378\u8f7d\u524d\u7acb\u5373\u88ab\u8c03\u7528\u3002\u540c\u6837\uff0c\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u6ce8\u610f\uff0c_PG_fini \u53ea\u4f1a\u5728\u5378\u8f7d\u6587\u4ef6\u65f6\u88ab\u8c03\u7528\uff0c\u800c\u4e0d\u4f1a\u5728\u8fdb\u7a0b\u7ec8\u6b62\u65f6\u88ab\u8c03\u7528\u3002\uff08\u76ee\u524d\uff0c\u5378\u8f7d\u5df2\u88ab\u7981\u7528\uff0c\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\uff0c\u4f46\u5c06\u6765\u53ef\u80fd\u4f1a\u6539\u53d8\u3002\uff09

\n
\n
\n
\n
\n
\n

37.9.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u4e0e\u51fd\u6570\u4f20\u9012\u5b83\u4eec\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a037.1\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a037.10\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a037.1\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a037.1.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
abstimeAbsoluteTimeutils/nabstime.h
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
reltimeRelativeTimeutils/nabstime.h
texttext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
tintervalTimeIntervalutils/nabstime.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n
\n
\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

37.9.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n\n#ifdef PG_MODULE_MAGIC\nPG_MODULE_MAGIC;\n#endif\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy((void *) VARDATA(new_t), /* destination */\n           (void *) VARDATA_ANY(t), /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a037.9.8\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a038\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a055\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

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\n
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37.9.4. \u7f16\u5199\u4ee3\u7801

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\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a037.9.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a037.9.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
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37.9.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

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\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 3.0 \u7248\u8d77\u9002\u7528\u3002

\n
\n
HP-UX
\n
\n

\u751f\u6210 PIC \u7684\u7cfb\u7edf\u7f16\u8bd1\u5668\u9009\u9879\u662f +z\u3002\u4f7f\u7528 GCC \u65f6\u5219\u662f -fPIC\u3002\u7528\u4e8e\u5171\u4eab\u5e93\u7684\u94fe\u63a5\u5668\u9009\u9879\u662f -b\u3002\u56e0\u6b64\uff1a

\n
cc +z -c foo.c\n
\n

\u6216\u8005\uff1a

\n
gcc -fPIC -c foo.c\n
\n

\u7136\u540e\uff1a

\n
ld -b -o foo.sl foo.o\n
\n

HP-UX \u4f7f\u7528 .sl \u4f5c\u4e3a\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff0c\u8fd9\u4e0e\u5927\u591a\u6570\u5176\u4ed6\u7cfb\u7edf\u4e0d\u540c\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a037.9.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

37.9.6. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u7f16\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u5982\u4e0b\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\n#ifdef PG_MODULE_MAGIC\nPG_MODULE_MAGIC;\n#endif\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u5b8f\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

37.9.7. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

37.9.8. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to result slot\n     *\n     * This is obsolete and only present for backward compatibility, viz,\n     * user-defined SRFs that use the deprecated TupleDescGetSlot().\n     */\n    TupleTableSlot *slot;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_UINT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

37.9.9. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u591a\u6001\u7c7b\u578b anyelement\u3001anyarray\u3001anynonarray\u3001anyenum \u548c anyrange\u3002\u5173\u4e8e\u591a\u6001\u51fd\u6570\u7684\u66f4\u8be6\u7ec6\u89e3\u91ca\uff0c\u89c1\u7b2c\u00a037.2.5\u00a0\u8282\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

37.9.10. \u8f6c\u6362\u51fd\u6570

\n
\n
\n
\n

\u67d0\u4e9b\u51fd\u6570\u8c03\u7528\u53ef\u4ee5\u5728\u89c4\u5212\u671f\u95f4\u6839\u636e\u51fd\u6570\u7279\u6709\u7684\u5c5e\u6027\u8fdb\u884c\u7b80\u5316\u3002\u4f8b\u5982\uff0cint4mul(n, 1) \u53ef\u4ee5\u76f4\u63a5\u7b80\u5316\u4e3a n\u3002\u8981\u5b9a\u4e49\u8fd9\u7c7b\u9488\u5bf9\u7279\u5b9a\u51fd\u6570\u7684\u4f18\u5316\uff0c\u8bf7\u7f16\u5199\u4e00\u4e2a\u8f6c\u6362\u51fd\u6570\uff0c\u5e76\u5c06\u5176 OID \u653e\u5165\u4e3b\u51fd\u6570\u7684 protransform \u5b57\u6bb5\u4e2d\uff0c\u8be5\u5b57\u6bb5\u4f4d\u4e8e\u5176 pg_proc \u9879\u4e2d\u3002\u8f6c\u6362\u51fd\u6570\u5fc5\u987b\u5177\u6709 SQL \u7b7e\u540d protransform(internal) RETURNS internal\u3002\u53c2\u6570\u5b9e\u9645\u4e0a\u662f FuncExpr *\uff0c\u5b83\u662f\u4e00\u4e2a\u8868\u793a\u4e3b\u51fd\u6570\u8c03\u7528\u7684\u5360\u4f4d\u8282\u70b9\u3002\u5982\u679c\u8f6c\u6362\u51fd\u6570\u5bf9\u8868\u8fbe\u5f0f\u6811\u7684\u5206\u6790\u8bc1\u660e\uff0c\u53ef\u4ee5\u7528\u7b80\u5316\u7684\u8868\u8fbe\u5f0f\u6811\u66ff\u4ee3\u5b83\u6240\u8868\u793a\u7684\u6240\u6709\u53ef\u80fd\u7684\u5177\u4f53\u8c03\u7528\uff0c\u5c31\u6784\u5efa\u5e76\u8fd4\u56de\u8be5\u7b80\u5316\u8868\u8fbe\u5f0f\u3002\u5426\u5219\uff0c\u8fd4\u56de\u4e00\u4e2a NULL \u6307\u9488\uff08\u4e0d\u662f SQL \u7a7a\u503c\uff09\u3002

\n

\u6211\u4eec\u4e0d\u4fdd\u8bc1 PostgreSQL \u5728\u8f6c\u6362\u51fd\u6570\u53ef\u4ee5\u7b80\u5316\u7684\u60c5\u51b5\u4e0b\u7edd\u4e0d\u4f1a\u8c03\u7528\u4e3b\u51fd\u6570\u3002\u8bf7\u786e\u4fdd\u7b80\u5316\u540e\u7684\u8868\u8fbe\u5f0f\u4e0e\u5b9e\u9645\u8c03\u7528\u4e3b\u51fd\u6570\u4e25\u683c\u7b49\u4ef7\u3002

\n

\u76ee\u524d\uff0c\u51fa\u4e8e\u5b89\u5168\u8003\u8651\uff0c\u8fd9\u9879\u529f\u80fd\u6ca1\u6709\u5728 SQL \u5c42\u9762\u5f00\u653e\u7ed9\u7528\u6237\uff0c\u56e0\u6b64\u5b9e\u9645\u53ea\u80fd\u7528\u4e8e\u4f18\u5316\u5185\u7f6e\u51fd\u6570\u3002

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37.9.11. \u5171\u4eab\u5185\u5b58\u4e0e LWLocks

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\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLock \u548c\u4e00\u5757\u5171\u4eab\u5185\u5b58\u3002\u9644\u52a0\u6a21\u5757\u7684\u5171\u4eab\u5e93\u5fc5\u987b\u901a\u8fc7\u5728\u4ee5\u4e0b\u53c2\u6570\u4e2d\u6307\u5b9a\u5b83\u6765\u9884\u88c5\u8f7d\uff1ashared_preload_libraries\u3002\u5171\u4eab\u5185\u5b58\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u7684\u8c03\u7528\u6765\u9884\u7559\uff1a

\n
void RequestAddinShmemSpace(int size)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728\u4f60\u7684 _PG_init \u51fd\u6570\u4e2d\u3002

\n

\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728 _PG_init \u4e2d\u3002\u8fd9\u6837\u53ef\u4ee5\u786e\u4fdd\u4e00\u4e2a\u5305\u542b num_lwlocks \u4e2a LWLock \u7684\u6570\u7ec4\u53ef\u901a\u8fc7\u4ee5\u4e0b\u540d\u79f0\u8bbf\u95ee\uff1atranche_name\u3002\u4f7f\u7528 GetNamedLWLockTranche \u53ef\u4ee5\u53d6\u5f97\u6307\u5411\u8be5\u6570\u7ec4\u7684\u6307\u9488\u3002

\n

\u4e3a\u907f\u514d\u7ade\u6001\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u9644\u52a0\u5230\u5176\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u5e76\u8fdb\u884c\u521d\u59cb\u5316\u65f6\uff0c\u90fd\u5e94\u4f7f\u7528\u8f7b\u91cf\u7ea7\u9501 AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\n\nif (!ptr)\n{\n        bool    found;\n\n        LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\n        ptr = ShmemInitStruct(\"my struct name\", size, &found);\n        if (!found)\n        {\n                initialize contents of shmem area;\n                acquire any requested LWLocks using:\n                ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n        }\n        LWLockRelease(AddinShmemInitLock);\n}\n
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37.9.12. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

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\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

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\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

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    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
", "manual_path": "/docs/10/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/10/xfunc-c.html", "method": "same-major semantic node", "sha256": "0df98937379292051379860f0a86609d1855b9c9df04dfb53c02ec0380079453", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/p[10]", "#XFUNC-C/div[10]/p[1]", "#XFUNC-C/div[10]/p[2]", "#XFUNC-C/div[10]/p[6]", "#XFUNC-C/div[10]/p[7]", "#XFUNC-C/div[10]/p[8]", "#XFUNC-C/div[11]/div[7]/p[1]", "#XFUNC-C/div[11]/div[8]/p[1]", "#XFUNC-C/div[11]/p[11]", "#XFUNC-C/div[11]/p[13]", "#XFUNC-C/div[11]/p[14]", "#XFUNC-C/div[11]/p[16]", "#XFUNC-C/div[11]/p[18]", "#XFUNC-C/div[11]/p[19]", "#XFUNC-C/div[11]/p[1]", "#XFUNC-C/div[11]/p[21]", "#XFUNC-C/div[11]/p[22]", "#XFUNC-C/div[11]/p[24]", "#XFUNC-C/div[11]/p[25]", "#XFUNC-C/div[11]/p[27]", "#XFUNC-C/div[11]/p[28]", "#XFUNC-C/div[11]/p[3]", "#XFUNC-C/div[11]/p[4]", "#XFUNC-C/div[11]/p[6]", "#XFUNC-C/div[11]/p[9]", "#XFUNC-C/div[12]/div[19]/p[1]", 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"#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[13]", "#XFUNC-C/div[5]/p[14]", "#XFUNC-C/div[5]/p[19]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[1]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[4]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[12]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[14]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[4]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[6]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[5]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[7]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[9]/p[0]", "#XFUNC-C/div[9]/div[6]/h3[0]", "#XFUNC-C/div[9]/div[6]/p[1]", "#XFUNC-C/div[9]/p[1]", "#XFUNC-C/div[9]/p[2]", "#XFUNC-C/div[9]/p[4]", "#XFUNC-C/div[9]/p[7]", "#XFUNC-C/div[9]/p[8]", "#XFUNC-C/p[3]"]}], "language": "zh", "original_text": {"/versions/10/description/0": "dynamically-loaded C functions", "/versions/10/facts/0/label": "Kind", "/versions/10/facts/0/value": "Native function language", "/versions/10/facts/1/label": "Trusted", "/versions/10/facts/2/label": 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"label": "11.22", "major": "11", "channel": "historical", "revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0", "source_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0", "catalog_fingerprint": "8f21f4444b7f68923f4762af0eb7937fa2907026e91249483e79050de012c901"}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "label": "Matching PostgreSQL source archive", "sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, {"url": "https://pg.center/docs/11/xfunc-c.html", "path": "xfunc-c.html", "label": "PostgreSQL 11 English manual", "sha256": "9e1cd39e5b6e7b390fd9b89de261253773c874a029e0a7369932ac5c75211b2c", "language": "en", "original_url": "/docs/11/xfunc-c.html"}], "sections": [], "signature": "", "attributes": {"kind": "Native function language", "handler": "", "trusted": "f", "validator": "fmgr_c_validator"}, "description": ["\u52a8\u6001\u52a0\u8f7d\u7684 C \u51fd\u6570"], "manual_html": "
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38.10.\u00a0C \u8bed\u8a00\u51fd\u6570

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\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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\n

38.10.1. \u52a8\u6001\u8f7d\u5165

\n
\n
\n
\n

\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u901a\u8fc7\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a038.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u9009\u62e9\u5305\u542b\u521d\u59cb\u5316\u548c\u7ec8\u7ed3\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u88c5\u8f7d\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_fini \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u5378\u8f7d\u524d\u7acb\u5373\u88ab\u8c03\u7528\u3002\u540c\u6837\uff0c\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u6ce8\u610f\uff0c_PG_fini \u53ea\u4f1a\u5728\u5378\u8f7d\u6587\u4ef6\u65f6\u88ab\u8c03\u7528\uff0c\u800c\u4e0d\u4f1a\u5728\u8fdb\u7a0b\u7ec8\u6b62\u65f6\u88ab\u8c03\u7528\u3002\uff08\u76ee\u524d\uff0c\u5378\u8f7d\u5df2\u88ab\u7981\u7528\uff0c\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\uff0c\u4f46\u5c06\u6765\u53ef\u80fd\u4f1a\u6539\u53d8\u3002\uff09

\n
\n
\n
\n
\n
\n

38.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u4e0e\u51fd\u6570\u4f20\u9012\u5b83\u4eec\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a038.1\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a038.11\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a038.1\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a038.1.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
abstimeAbsoluteTimeutils/nabstime.h
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
reltimeRelativeTimeutils/nabstime.h
texttext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
tintervalTimeIntervalutils/nabstime.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

38.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy((void *) VARDATA(new_t), /* destination */\n           (void *) VARDATA_ANY(t), /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a038.10.8\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a039\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a056\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

\n
\n
\n
\n
\n
\n

38.10.4. \u7f16\u5199\u4ee3\u7801

\n
\n
\n
\n

\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a038.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a038.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

38.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 3.0 \u7248\u8d77\u9002\u7528\u3002

\n
\n
HP-UX
\n
\n

\u751f\u6210 PIC \u7684\u7cfb\u7edf\u7f16\u8bd1\u5668\u9009\u9879\u662f +z\u3002\u4f7f\u7528 GCC \u65f6\u5219\u662f -fPIC\u3002\u7528\u4e8e\u5171\u4eab\u5e93\u7684\u94fe\u63a5\u5668\u9009\u9879\u662f -b\u3002\u56e0\u6b64\uff1a

\n
cc +z -c foo.c\n
\n

\u6216\u8005\uff1a

\n
gcc -fPIC -c foo.c\n
\n

\u7136\u540e\uff1a

\n
ld -b -o foo.sl foo.o\n
\n

HP-UX \u4f7f\u7528 .sl \u4f5c\u4e3a\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff0c\u8fd9\u4e0e\u5927\u591a\u6570\u5176\u4ed6\u7cfb\u7edf\u4e0d\u540c\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a038.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

38.10.6. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u5b8f\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

38.10.7. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

38.10.8. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to result slot\n     *\n     * This is obsolete and only present for backward compatibility, viz,\n     * user-defined SRFs that use the deprecated TupleDescGetSlot().\n     */\n    TupleTableSlot *slot;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_UINT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

38.10.9. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u591a\u6001\u7c7b\u578b anyelement\u3001anyarray\u3001anynonarray\u3001anyenum \u548c anyrange\u3002\u5173\u4e8e\u591a\u6001\u51fd\u6570\u7684\u66f4\u8be6\u7ec6\u89e3\u91ca\uff0c\u89c1\u7b2c\u00a038.2.5\u00a0\u8282\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

38.10.10. \u8f6c\u6362\u51fd\u6570

\n
\n
\n
\n

\u67d0\u4e9b\u51fd\u6570\u8c03\u7528\u53ef\u4ee5\u5728\u89c4\u5212\u671f\u95f4\u6839\u636e\u51fd\u6570\u7279\u6709\u7684\u5c5e\u6027\u8fdb\u884c\u7b80\u5316\u3002\u4f8b\u5982\uff0cint4mul(n, 1) \u53ef\u4ee5\u76f4\u63a5\u7b80\u5316\u4e3a n\u3002\u8981\u5b9a\u4e49\u8fd9\u7c7b\u9488\u5bf9\u7279\u5b9a\u51fd\u6570\u7684\u4f18\u5316\uff0c\u8bf7\u7f16\u5199\u4e00\u4e2a\u8f6c\u6362\u51fd\u6570\uff0c\u5e76\u5c06\u5176 OID \u653e\u5165\u4e3b\u51fd\u6570\u7684 protransform \u5b57\u6bb5\u4e2d\uff0c\u8be5\u5b57\u6bb5\u4f4d\u4e8e\u5176 pg_proc \u9879\u4e2d\u3002\u8f6c\u6362\u51fd\u6570\u5fc5\u987b\u5177\u6709 SQL \u7b7e\u540d protransform(internal) RETURNS internal\u3002\u53c2\u6570\u5b9e\u9645\u4e0a\u662f FuncExpr *\uff0c\u5b83\u662f\u4e00\u4e2a\u8868\u793a\u4e3b\u51fd\u6570\u8c03\u7528\u7684\u5360\u4f4d\u8282\u70b9\u3002\u5982\u679c\u8f6c\u6362\u51fd\u6570\u5bf9\u8868\u8fbe\u5f0f\u6811\u7684\u5206\u6790\u8bc1\u660e\uff0c\u53ef\u4ee5\u7528\u7b80\u5316\u7684\u8868\u8fbe\u5f0f\u6811\u66ff\u4ee3\u5b83\u6240\u8868\u793a\u7684\u6240\u6709\u53ef\u80fd\u7684\u5177\u4f53\u8c03\u7528\uff0c\u5c31\u6784\u5efa\u5e76\u8fd4\u56de\u8be5\u7b80\u5316\u8868\u8fbe\u5f0f\u3002\u5426\u5219\uff0c\u8fd4\u56de\u4e00\u4e2a NULL \u6307\u9488\uff08\u4e0d\u662f SQL \u7a7a\u503c\uff09\u3002

\n

\u6211\u4eec\u4e0d\u4fdd\u8bc1 PostgreSQL \u5728\u8f6c\u6362\u51fd\u6570\u53ef\u4ee5\u7b80\u5316\u7684\u60c5\u51b5\u4e0b\u7edd\u4e0d\u4f1a\u8c03\u7528\u4e3b\u51fd\u6570\u3002\u8bf7\u786e\u4fdd\u7b80\u5316\u540e\u7684\u8868\u8fbe\u5f0f\u4e0e\u5b9e\u9645\u8c03\u7528\u4e3b\u51fd\u6570\u4e25\u683c\u7b49\u4ef7\u3002

\n

\u76ee\u524d\uff0c\u51fa\u4e8e\u5b89\u5168\u8003\u8651\uff0c\u8fd9\u9879\u529f\u80fd\u6ca1\u6709\u5728 SQL \u5c42\u9762\u5f00\u653e\u7ed9\u7528\u6237\uff0c\u56e0\u6b64\u5b9e\u9645\u53ea\u80fd\u7528\u4e8e\u4f18\u5316\u5185\u7f6e\u51fd\u6570\u3002

\n
\n
\n
\n
\n
\n

38.10.11. \u5171\u4eab\u5185\u5b58\u4e0e LWLocks

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLock \u548c\u4e00\u5757\u5171\u4eab\u5185\u5b58\u3002\u9644\u52a0\u6a21\u5757\u7684\u5171\u4eab\u5e93\u5fc5\u987b\u901a\u8fc7\u5728\u4ee5\u4e0b\u53c2\u6570\u4e2d\u6307\u5b9a\u5b83\u6765\u9884\u88c5\u8f7d\uff1ashared_preload_libraries\u3002\u5171\u4eab\u5185\u5b58\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u7684\u8c03\u7528\u6765\u9884\u7559\uff1a

\n
void RequestAddinShmemSpace(int size)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728\u4f60\u7684 _PG_init \u51fd\u6570\u4e2d\u3002

\n

\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728 _PG_init \u4e2d\u3002\u8fd9\u6837\u53ef\u4ee5\u786e\u4fdd\u4e00\u4e2a\u5305\u542b num_lwlocks \u4e2a LWLock \u7684\u6570\u7ec4\u53ef\u901a\u8fc7\u4ee5\u4e0b\u540d\u79f0\u8bbf\u95ee\uff1atranche_name\u3002\u4f7f\u7528 GetNamedLWLockTranche \u53ef\u4ee5\u53d6\u5f97\u6307\u5411\u8be5\u6570\u7ec4\u7684\u6307\u9488\u3002

\n

\u4e3a\u907f\u514d\u7ade\u6001\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u9644\u52a0\u5230\u5176\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u5e76\u8fdb\u884c\u521d\u59cb\u5316\u65f6\uff0c\u90fd\u5e94\u4f7f\u7528\u8f7b\u91cf\u7ea7\u9501 AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\n\nif (!ptr)\n{\n        bool    found;\n\n        LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\n        ptr = ShmemInitStruct(\"my struct name\", size, &found);\n        if (!found)\n        {\n                initialize contents of shmem area;\n                acquire any requested LWLocks using:\n                ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n        }\n        LWLockRelease(AddinShmemInitLock);\n}\n
\n
\n
\n
\n
\n
\n

38.10.12. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
", "manual_path": "/docs/11/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/11/xfunc-c.html", "method": "same-major semantic node", "sha256": "338b6447b1144585971c12bdf32b24efc4b9b5a4778aff31b878afd575c1c68c", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/p[10]", "#XFUNC-C/div[10]/p[1]", "#XFUNC-C/div[10]/p[2]", "#XFUNC-C/div[10]/p[6]", "#XFUNC-C/div[10]/p[7]", "#XFUNC-C/div[10]/p[8]", "#XFUNC-C/div[11]/div[7]/p[1]", "#XFUNC-C/div[11]/div[8]/p[1]", "#XFUNC-C/div[11]/p[11]", "#XFUNC-C/div[11]/p[13]", "#XFUNC-C/div[11]/p[14]", "#XFUNC-C/div[11]/p[16]", "#XFUNC-C/div[11]/p[18]", "#XFUNC-C/div[11]/p[19]", "#XFUNC-C/div[11]/p[1]", "#XFUNC-C/div[11]/p[21]", "#XFUNC-C/div[11]/p[22]", "#XFUNC-C/div[11]/p[24]", "#XFUNC-C/div[11]/p[25]", "#XFUNC-C/div[11]/p[27]", "#XFUNC-C/div[11]/p[28]", "#XFUNC-C/div[11]/p[3]", "#XFUNC-C/div[11]/p[4]", "#XFUNC-C/div[11]/p[6]", "#XFUNC-C/div[11]/p[9]", "#XFUNC-C/div[12]/div[19]/p[1]", "#XFUNC-C/div[12]/p[10]", "#XFUNC-C/div[12]/p[12]", "#XFUNC-C/div[12]/p[13]", "#XFUNC-C/div[12]/p[15]", "#XFUNC-C/div[12]/p[20]", "#XFUNC-C/div[12]/p[22]", "#XFUNC-C/div[12]/p[24]", "#XFUNC-C/div[12]/p[26]", "#XFUNC-C/div[12]/p[28]", "#XFUNC-C/div[12]/p[2]", "#XFUNC-C/div[12]/p[3]", "#XFUNC-C/div[12]/p[4]", "#XFUNC-C/div[12]/p[6]", "#XFUNC-C/div[12]/p[8]", "#XFUNC-C/div[13]/p[1]", "#XFUNC-C/div[13]/p[2]", "#XFUNC-C/div[13]/p[4]", "#XFUNC-C/div[13]/p[6]", "#XFUNC-C/div[14]/p[1]", "#XFUNC-C/div[14]/p[2]", "#XFUNC-C/div[14]/p[3]", "#XFUNC-C/div[15]/p[1]", "#XFUNC-C/div[15]/p[3]", "#XFUNC-C/div[15]/p[6]", "#XFUNC-C/div[16]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[16]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[16]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[16]/p[2]", "#XFUNC-C/div[16]/p[4]", "#XFUNC-C/div[1]/dl[0]/dt[0]", "#XFUNC-C/div[1]/dl[0]/dt[10]", "#XFUNC-C/div[1]/dl[0]/dt[11]", "#XFUNC-C/div[1]/dl[0]/dt[1]", "#XFUNC-C/div[1]/dl[0]/dt[2]", "#XFUNC-C/div[1]/dl[0]/dt[3]", "#XFUNC-C/div[1]/dl[0]/dt[4]", "#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[11]", "#XFUNC-C/div[5]/p[13]", "#XFUNC-C/div[5]/p[18]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[1]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[4]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[12]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[14]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[4]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[6]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[5]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[7]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[9]/p[0]", "#XFUNC-C/div[9]/div[6]/h3[0]", "#XFUNC-C/div[9]/div[6]/p[1]", "#XFUNC-C/div[9]/p[1]", "#XFUNC-C/div[9]/p[2]", "#XFUNC-C/div[9]/p[4]", "#XFUNC-C/div[9]/p[7]", "#XFUNC-C/div[9]/p[8]", "#XFUNC-C/p[3]"]}], "language": "zh", "original_text": {"/versions/11/description/0": "dynamically-loaded C functions", "/versions/11/facts/0/label": "Kind", "/versions/11/facts/0/value": "Native function language", "/versions/11/facts/1/label": "Trusted", "/versions/11/facts/2/label": 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\u51fd\u6570"], "manual_html": "
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37.10.\u00a0C \u8bed\u8a00\u51fd\u6570

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\n
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\n

\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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37.10.1. \u52a8\u6001\u8f7d\u5165

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\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
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    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u901a\u8fc7\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a037.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u9009\u62e9\u5305\u542b\u521d\u59cb\u5316\u548c\u7ec8\u7ed3\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u88c5\u8f7d\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_fini \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u5378\u8f7d\u524d\u7acb\u5373\u88ab\u8c03\u7528\u3002\u540c\u6837\uff0c\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u6ce8\u610f\uff0c_PG_fini \u53ea\u4f1a\u5728\u5378\u8f7d\u6587\u4ef6\u65f6\u88ab\u8c03\u7528\uff0c\u800c\u4e0d\u4f1a\u5728\u8fdb\u7a0b\u7ec8\u6b62\u65f6\u88ab\u8c03\u7528\u3002\uff08\u76ee\u524d\uff0c\u5378\u8f7d\u5df2\u88ab\u7981\u7528\uff0c\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\uff0c\u4f46\u5c06\u6765\u53ef\u80fd\u4f1a\u6539\u53d8\u3002\uff09

\n
\n
\n
\n
\n
\n

37.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u4e0e\u51fd\u6570\u4f20\u9012\u5b83\u4eec\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a037.1\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a037.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a037.1\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a037.1.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
texttext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

37.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy((void *) VARDATA(new_t), /* destination */\n           (void *) VARDATA_ANY(t), /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a037.10.8\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a038\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a055\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

\n
\n
\n
\n
\n
\n

37.10.4. \u7f16\u5199\u4ee3\u7801

\n
\n
\n
\n

\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a037.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a037.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

37.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 3.0 \u7248\u8d77\u9002\u7528\u3002

\n
\n
HP-UX
\n
\n

\u751f\u6210 PIC \u7684\u7cfb\u7edf\u7f16\u8bd1\u5668\u9009\u9879\u662f +z\u3002\u4f7f\u7528 GCC \u65f6\u5219\u662f -fPIC\u3002\u7528\u4e8e\u5171\u4eab\u5e93\u7684\u94fe\u63a5\u5668\u9009\u9879\u662f -b\u3002\u56e0\u6b64\uff1a

\n
cc +z -c foo.c\n
\n

\u6216\u8005\uff1a

\n
gcc -fPIC -c foo.c\n
\n

\u7136\u540e\uff1a

\n
ld -b -o foo.sl foo.o\n
\n

HP-UX \u4f7f\u7528 .sl \u4f5c\u4e3a\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff0c\u8fd9\u4e0e\u5927\u591a\u6570\u5176\u4ed6\u7cfb\u7edf\u4e0d\u540c\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a037.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

37.10.6. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u5b8f\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

37.10.7. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

37.10.8. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_UINT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

37.10.9. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u591a\u6001\u7c7b\u578b anyelement\u3001anyarray\u3001anynonarray\u3001anyenum \u548c anyrange\u3002\u5173\u4e8e\u591a\u6001\u51fd\u6570\u7684\u66f4\u8be6\u7ec6\u89e3\u91ca\uff0c\u89c1\u7b2c\u00a037.2.5\u00a0\u8282\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

37.10.10. \u5171\u4eab\u5185\u5b58\u4e0e LWLocks

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLock \u548c\u4e00\u5757\u5171\u4eab\u5185\u5b58\u3002\u9644\u52a0\u6a21\u5757\u7684\u5171\u4eab\u5e93\u5fc5\u987b\u901a\u8fc7\u5728\u4ee5\u4e0b\u53c2\u6570\u4e2d\u6307\u5b9a\u5b83\u6765\u9884\u88c5\u8f7d\uff1ashared_preload_libraries\u3002\u5171\u4eab\u5185\u5b58\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u7684\u8c03\u7528\u6765\u9884\u7559\uff1a

\n
void RequestAddinShmemSpace(int size)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728\u4f60\u7684 _PG_init \u51fd\u6570\u4e2d\u3002

\n

\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728 _PG_init \u4e2d\u3002\u8fd9\u6837\u53ef\u4ee5\u786e\u4fdd\u4e00\u4e2a\u5305\u542b num_lwlocks \u4e2a LWLock \u7684\u6570\u7ec4\u53ef\u901a\u8fc7\u4ee5\u4e0b\u540d\u79f0\u8bbf\u95ee\uff1atranche_name\u3002\u4f7f\u7528 GetNamedLWLockTranche \u53ef\u4ee5\u53d6\u5f97\u6307\u5411\u8be5\u6570\u7ec4\u7684\u6307\u9488\u3002

\n

\u4e3a\u907f\u514d\u7ade\u6001\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u9644\u52a0\u5230\u5176\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u5e76\u8fdb\u884c\u521d\u59cb\u5316\u65f6\uff0c\u90fd\u5e94\u4f7f\u7528\u8f7b\u91cf\u7ea7\u9501 AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\n\nif (!ptr)\n{\n        bool    found;\n\n        LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\n        ptr = ShmemInitStruct(\"my struct name\", size, &found);\n        if (!found)\n        {\n                initialize contents of shmem area;\n                acquire any requested LWLocks using:\n                ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n        }\n        LWLockRelease(AddinShmemInitLock);\n}\n
\n
\n
\n
\n
\n
\n

37.10.11. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
", "manual_path": "/docs/12/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/12/xfunc-c.html", "method": "same-major semantic node", "sha256": "b25a73df45087a8fdc374e82b6439c1e121ac685f86ab05f852f86fb2d32f749", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/p[10]", "#XFUNC-C/div[10]/p[1]", "#XFUNC-C/div[10]/p[2]", "#XFUNC-C/div[10]/p[6]", "#XFUNC-C/div[10]/p[7]", "#XFUNC-C/div[10]/p[8]", "#XFUNC-C/div[11]/div[7]/p[1]", "#XFUNC-C/div[11]/div[8]/p[1]", "#XFUNC-C/div[11]/p[11]", "#XFUNC-C/div[11]/p[13]", "#XFUNC-C/div[11]/p[14]", "#XFUNC-C/div[11]/p[16]", "#XFUNC-C/div[11]/p[18]", "#XFUNC-C/div[11]/p[19]", "#XFUNC-C/div[11]/p[1]", "#XFUNC-C/div[11]/p[21]", "#XFUNC-C/div[11]/p[22]", "#XFUNC-C/div[11]/p[24]", "#XFUNC-C/div[11]/p[25]", "#XFUNC-C/div[11]/p[27]", "#XFUNC-C/div[11]/p[28]", "#XFUNC-C/div[11]/p[3]", "#XFUNC-C/div[11]/p[4]", "#XFUNC-C/div[11]/p[6]", "#XFUNC-C/div[11]/p[9]", "#XFUNC-C/div[12]/div[19]/p[1]", "#XFUNC-C/div[12]/p[10]", "#XFUNC-C/div[12]/p[12]", "#XFUNC-C/div[12]/p[13]", "#XFUNC-C/div[12]/p[15]", "#XFUNC-C/div[12]/p[20]", "#XFUNC-C/div[12]/p[22]", "#XFUNC-C/div[12]/p[24]", "#XFUNC-C/div[12]/p[26]", "#XFUNC-C/div[12]/p[28]", "#XFUNC-C/div[12]/p[2]", "#XFUNC-C/div[12]/p[3]", "#XFUNC-C/div[12]/p[4]", "#XFUNC-C/div[12]/p[6]", "#XFUNC-C/div[12]/p[8]", "#XFUNC-C/div[13]/p[1]", "#XFUNC-C/div[13]/p[2]", "#XFUNC-C/div[13]/p[4]", "#XFUNC-C/div[13]/p[6]", "#XFUNC-C/div[14]/p[1]", "#XFUNC-C/div[14]/p[3]", "#XFUNC-C/div[14]/p[6]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[15]/p[2]", "#XFUNC-C/div[15]/p[4]", "#XFUNC-C/div[1]/dl[0]/dt[0]", "#XFUNC-C/div[1]/dl[0]/dt[10]", "#XFUNC-C/div[1]/dl[0]/dt[1]", "#XFUNC-C/div[1]/dl[0]/dt[2]", "#XFUNC-C/div[1]/dl[0]/dt[3]", "#XFUNC-C/div[1]/dl[0]/dt[4]", "#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[11]", "#XFUNC-C/div[5]/p[13]", "#XFUNC-C/div[5]/p[18]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[0]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[3]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[12]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[14]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[4]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[6]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[5]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[7]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[9]/p[0]", "#XFUNC-C/div[9]/div[6]/h3[0]", "#XFUNC-C/div[9]/div[6]/p[1]", "#XFUNC-C/div[9]/p[1]", "#XFUNC-C/div[9]/p[2]", "#XFUNC-C/div[9]/p[4]", "#XFUNC-C/div[9]/p[7]", "#XFUNC-C/div[9]/p[8]", "#XFUNC-C/p[3]"]}], "language": "zh", "original_text": {"/versions/12/description/0": "dynamically-loaded C functions", "/versions/12/facts/0/label": "Kind", "/versions/12/facts/0/value": "Native function language", "/versions/12/facts/1/label": "Trusted", "/versions/12/facts/2/label": "Validator"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": 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37.10.\u00a0C \u8bed\u8a00\u51fd\u6570

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\n

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\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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37.10.1. \u52a8\u6001\u8f7d\u5165

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\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u901a\u8fc7\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a037.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u9009\u62e9\u5305\u542b\u521d\u59cb\u5316\u548c\u7ec8\u7ed3\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u88c5\u8f7d\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_fini \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u5378\u8f7d\u524d\u7acb\u5373\u88ab\u8c03\u7528\u3002\u540c\u6837\uff0c\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u6ce8\u610f\uff0c_PG_fini \u53ea\u4f1a\u5728\u5378\u8f7d\u6587\u4ef6\u65f6\u88ab\u8c03\u7528\uff0c\u800c\u4e0d\u4f1a\u5728\u8fdb\u7a0b\u7ec8\u6b62\u65f6\u88ab\u8c03\u7528\u3002\uff08\u76ee\u524d\uff0c\u5378\u8f7d\u5df2\u88ab\u7981\u7528\uff0c\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\uff0c\u4f46\u5c06\u6765\u53ef\u80fd\u4f1a\u6539\u53d8\u3002\uff09

\n
\n
\n
\n
\n
\n

37.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u4e0e\u51fd\u6570\u4f20\u9012\u5b83\u4eec\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a037.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a037.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a037.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a037.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
texttext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

37.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy((void *) VARDATA(new_t), /* destination */\n           (void *) VARDATA_ANY(t), /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a037.10.8\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a038\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a055\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

\n
\n
\n
\n
\n
\n

37.10.4. \u7f16\u5199\u4ee3\u7801

\n
\n
\n
\n

\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a037.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a037.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

37.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 3.0 \u7248\u8d77\u9002\u7528\u3002

\n
\n
HP-UX
\n
\n

\u751f\u6210 PIC \u7684\u7cfb\u7edf\u7f16\u8bd1\u5668\u9009\u9879\u662f +z\u3002\u4f7f\u7528 GCC \u65f6\u5219\u662f -fPIC\u3002\u7528\u4e8e\u5171\u4eab\u5e93\u7684\u94fe\u63a5\u5668\u9009\u9879\u662f -b\u3002\u56e0\u6b64\uff1a

\n
cc +z -c foo.c\n
\n

\u6216\u8005\uff1a

\n
gcc -fPIC -c foo.c\n
\n

\u7136\u540e\uff1a

\n
ld -b -o foo.sl foo.o\n
\n

HP-UX \u4f7f\u7528 .sl \u4f5c\u4e3a\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff0c\u8fd9\u4e0e\u5927\u591a\u6570\u5176\u4ed6\u7cfb\u7edf\u4e0d\u540c\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a037.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

37.10.6. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u5b8f\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

37.10.7. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

37.10.8. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_UINT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

37.10.9. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a037.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

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37.10.10. \u5171\u4eab\u5185\u5b58\u4e0e LWLocks

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\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLock \u548c\u4e00\u5757\u5171\u4eab\u5185\u5b58\u3002\u9644\u52a0\u6a21\u5757\u7684\u5171\u4eab\u5e93\u5fc5\u987b\u901a\u8fc7\u5728\u4ee5\u4e0b\u53c2\u6570\u4e2d\u6307\u5b9a\u5b83\u6765\u9884\u88c5\u8f7d\uff1ashared_preload_libraries\u3002\u5171\u4eab\u5185\u5b58\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u7684\u8c03\u7528\u6765\u9884\u7559\uff1a

\n
void RequestAddinShmemSpace(int size)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728\u4f60\u7684 _PG_init \u51fd\u6570\u4e2d\u3002

\n

\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728 _PG_init \u4e2d\u3002\u8fd9\u6837\u53ef\u4ee5\u786e\u4fdd\u4e00\u4e2a\u5305\u542b num_lwlocks \u4e2a LWLock \u7684\u6570\u7ec4\u53ef\u901a\u8fc7\u4ee5\u4e0b\u540d\u79f0\u8bbf\u95ee\uff1atranche_name\u3002\u4f7f\u7528 GetNamedLWLockTranche \u53ef\u4ee5\u53d6\u5f97\u6307\u5411\u8be5\u6570\u7ec4\u7684\u6307\u9488\u3002

\n

\u4e3a\u907f\u514d\u7ade\u6001\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u9644\u52a0\u5230\u5176\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u5e76\u8fdb\u884c\u521d\u59cb\u5316\u65f6\uff0c\u90fd\u5e94\u4f7f\u7528\u8f7b\u91cf\u7ea7\u9501 AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\n\nif (!ptr)\n{\n        bool    found;\n\n        LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\n        ptr = ShmemInitStruct(\"my struct name\", size, &found);\n        if (!found)\n        {\n                initialize contents of shmem area;\n                acquire any requested LWLocks using:\n                ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n        }\n        LWLockRelease(AddinShmemInitLock);\n}\n
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37.10.11. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

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\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

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\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

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    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

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", "manual_path": "/docs/13/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/13/xfunc-c.html", "method": "same-major semantic node", "sha256": "095469efa3baa961b27032ae79fbe7a17909a3ff9341e854497b97168d4a1271", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/p[10]", "#XFUNC-C/div[10]/p[1]", "#XFUNC-C/div[10]/p[2]", "#XFUNC-C/div[10]/p[6]", "#XFUNC-C/div[10]/p[7]", "#XFUNC-C/div[10]/p[8]", "#XFUNC-C/div[11]/div[7]/p[1]", "#XFUNC-C/div[11]/div[8]/p[1]", "#XFUNC-C/div[11]/p[11]", "#XFUNC-C/div[11]/p[13]", "#XFUNC-C/div[11]/p[14]", "#XFUNC-C/div[11]/p[16]", "#XFUNC-C/div[11]/p[18]", "#XFUNC-C/div[11]/p[19]", "#XFUNC-C/div[11]/p[1]", "#XFUNC-C/div[11]/p[21]", "#XFUNC-C/div[11]/p[22]", "#XFUNC-C/div[11]/p[24]", "#XFUNC-C/div[11]/p[25]", "#XFUNC-C/div[11]/p[27]", "#XFUNC-C/div[11]/p[28]", "#XFUNC-C/div[11]/p[3]", "#XFUNC-C/div[11]/p[4]", "#XFUNC-C/div[11]/p[6]", "#XFUNC-C/div[11]/p[9]", "#XFUNC-C/div[12]/div[19]/p[1]", 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"#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[11]", "#XFUNC-C/div[5]/p[13]", "#XFUNC-C/div[5]/p[18]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[0]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[3]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[12]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[14]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[4]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[6]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[5]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[7]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[9]/p[0]", "#XFUNC-C/div[9]/div[6]/h3[0]", "#XFUNC-C/div[9]/div[6]/p[1]", "#XFUNC-C/div[9]/p[1]", "#XFUNC-C/div[9]/p[2]", "#XFUNC-C/div[9]/p[4]", "#XFUNC-C/div[9]/p[7]", "#XFUNC-C/div[9]/p[8]", "#XFUNC-C/p[3]"]}], "language": "zh", "original_text": {"/versions/13/description/0": "dynamically-loaded C functions", "/versions/13/facts/0/label": "Kind", "/versions/13/facts/0/value": "Native function language", "/versions/13/facts/1/label": "Trusted", "/versions/13/facts/2/label": "Validator"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "d3a7e17f566a162b02902cbfe8f531ec14ac4d0136c9829f978e34d91a10e1a6"}, "comparison_data": {"kind": "Native function language", "handler": "", "trusted": "f", "validator": "fmgr_c_validator"}, "comparison_hash": "e8a219c1a26602affef41a21da26d099cf721ba42739cb7b056898c9e2d6fbe6", "manual_language": "zh"}, "14": {"facts": [{"label": "\u79cd\u7c7b", "value": "\u539f\u751f\u51fd\u6570\u8bed\u8a00"}, {"label": "\u53ef\u4fe1", "value": "f"}, {"label": "\u6821\u9a8c\u51fd\u6570", "value": "fmgr_c_validator"}], "tables": [], "aliases": [], "catalog": {"oid": "13", "descr": "dynamically-loaded C functions", "lanacl": "_null_", "lanispl": "f", "lanname": "c", "lanowner": "POSTGRES", "laninline": "0", "oid_symbol": "ClanguageId", "lanpltrusted": "f", "lanvalidator": "fmgr_c_validator", "lanplcallfoid": "0"}, "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "label": "14.24", "major": "14", "channel": "stable", "revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897", "source_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897", "catalog_fingerprint": "b272e6a82e4c46efda81c3a6a4cdf7de6a83dfff7f02f226a392fbe9acdd3adb"}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "label": "Matching PostgreSQL source archive", "sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, {"url": "https://pg.center/docs/14/xfunc-c.html", "path": "xfunc-c.html", "label": "PostgreSQL 14 English manual", "sha256": "7fd26810ad531d4158f3c87ccf1168c7b4b7b0763441b8912b525d7c20aef658", "language": "en", "original_url": "/docs/14/xfunc-c.html"}], "sections": [], "signature": "", "attributes": {"kind": "Native function language", "handler": "", "trusted": "f", "validator": "fmgr_c_validator"}, "description": ["\u52a8\u6001\u52a0\u8f7d\u7684 C \u51fd\u6570"], "manual_html": "
\n
\n
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\n

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38.10.\u00a0C \u8bed\u8a00\u51fd\u6570

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\n
\n

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\n
\n
\n

\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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38.10.1. \u52a8\u6001\u8f7d\u5165

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\n

\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u904d\u5386\u901a\u5f80\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a038.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u9009\u62e9\u5305\u542b\u521d\u59cb\u5316\u548c\u7ec8\u7ed3\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u88c5\u8f7d\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_fini \u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u4f1a\u5728\u6587\u4ef6\u5378\u8f7d\u524d\u7acb\u5373\u88ab\u8c03\u7528\u3002\u540c\u6837\uff0c\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u53c2\u6570\uff0c\u5e76\u4e14\u5e94\u8fd4\u56de void\u3002\u6ce8\u610f\uff0c_PG_fini \u53ea\u4f1a\u5728\u5378\u8f7d\u6587\u4ef6\u65f6\u88ab\u8c03\u7528\uff0c\u800c\u4e0d\u4f1a\u5728\u8fdb\u7a0b\u7ec8\u6b62\u65f6\u88ab\u8c03\u7528\u3002\uff08\u76ee\u524d\uff0c\u5378\u8f7d\u5df2\u88ab\u7981\u7528\uff0c\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\uff0c\u4f46\u5c06\u6765\u53ef\u80fd\u4f1a\u6539\u53d8\u3002\uff09

\n
\n
\n
\n
\n
\n

38.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u5c06\u5b83\u4eec\u4f20\u5165\u51fd\u6570\u548c\u4ece\u51fd\u6570\u4f20\u51fa\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a038.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a038.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a038.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a038.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
texttext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

38.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy((void *) VARDATA(new_t), /* destination */\n           (void *) VARDATA_ANY(t), /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a038.10.8\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a039\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a056\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

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38.10.4. \u7f16\u5199\u4ee3\u7801

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\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a038.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a038.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

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    • \n
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38.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

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\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 3.0 \u7248\u8d77\u9002\u7528\u3002

\n
\n
HP-UX
\n
\n

\u751f\u6210 PIC \u7684\u7cfb\u7edf\u7f16\u8bd1\u5668\u9009\u9879\u662f +z\u3002\u4f7f\u7528 GCC \u65f6\u5219\u662f -fPIC\u3002\u7528\u4e8e\u5171\u4eab\u5e93\u7684\u94fe\u63a5\u5668\u9009\u9879\u662f -b\u3002\u56e0\u6b64\uff1a

\n
cc +z -c foo.c\n
\n

\u6216\u8005\uff1a

\n
gcc -fPIC -c foo.c\n
\n

\u7136\u540e\uff1a

\n
ld -b -o foo.sl foo.o\n
\n

HP-UX \u4f7f\u7528 .sl \u4f5c\u4e3a\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff0c\u8fd9\u4e0e\u5927\u591a\u6570\u5176\u4ed6\u7cfb\u7edf\u4e0d\u540c\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a038.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

38.10.6. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u5b8f\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

38.10.7. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

38.10.8. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_UINT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

38.10.9. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a038.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

38.10.10. \u5171\u4eab\u5185\u5b58\u4e0e LWLocks

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLock \u548c\u4e00\u5757\u5171\u4eab\u5185\u5b58\u3002\u9644\u52a0\u6a21\u5757\u7684\u5171\u4eab\u5e93\u5fc5\u987b\u901a\u8fc7\u5728\u4ee5\u4e0b\u53c2\u6570\u4e2d\u6307\u5b9a\u5b83\u6765\u9884\u88c5\u8f7d\uff1ashared_preload_libraries\u3002\u5171\u4eab\u5185\u5b58\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u7684\u8c03\u7528\u6765\u9884\u7559\uff1a

\n
void RequestAddinShmemSpace(int size)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728\u4f60\u7684 _PG_init \u51fd\u6570\u4e2d\u3002

\n

\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8be5\u8c03\u7528\u5e94\u653e\u5728 _PG_init \u4e2d\u3002\u8fd9\u6837\u53ef\u4ee5\u786e\u4fdd\u4e00\u4e2a\u5305\u542b num_lwlocks \u4e2a LWLock \u7684\u6570\u7ec4\u53ef\u901a\u8fc7\u4ee5\u4e0b\u540d\u79f0\u8bbf\u95ee\uff1atranche_name\u3002\u4f7f\u7528 GetNamedLWLockTranche \u53ef\u4ee5\u53d6\u5f97\u6307\u5411\u8be5\u6570\u7ec4\u7684\u6307\u9488\u3002

\n

\u4e3a\u907f\u514d\u7ade\u6001\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u9644\u52a0\u5230\u5176\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u5e76\u8fdb\u884c\u521d\u59cb\u5316\u65f6\uff0c\u90fd\u5e94\u4f7f\u7528\u8f7b\u91cf\u7ea7\u9501 AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\n\nif (!ptr)\n{\n        bool    found;\n\n        LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\n        ptr = ShmemInitStruct(\"my struct name\", size, &found);\n        if (!found)\n        {\n                initialize contents of shmem area;\n                acquire any requested LWLocks using:\n                ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n        }\n        LWLockRelease(AddinShmemInitLock);\n}\n
\n
\n
\n
\n
\n
\n

38.10.11. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

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  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
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"#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[11]", "#XFUNC-C/div[5]/p[13]", "#XFUNC-C/div[5]/p[18]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[0]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[3]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[12]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[14]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[4]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[6]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[5]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[7]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[9]/p[0]", "#XFUNC-C/div[9]/div[6]/h3[0]", "#XFUNC-C/div[9]/div[6]/p[1]", "#XFUNC-C/div[9]/p[1]", "#XFUNC-C/div[9]/p[2]", "#XFUNC-C/div[9]/p[4]", "#XFUNC-C/div[9]/p[7]", "#XFUNC-C/div[9]/p[8]", "#XFUNC-C/p[3]"]}], "language": "zh", "original_text": {"/versions/14/description/0": "dynamically-loaded C functions", "/versions/14/facts/0/label": "Kind", "/versions/14/facts/0/value": "Native function language", "/versions/14/facts/1/label": "Trusted", "/versions/14/facts/2/label": "Validator"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": 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38.10.\u00a0C \u8bed\u8a00\u51fd\u6570

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\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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38.10.1. \u52a8\u6001\u8f7d\u5165

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\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

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    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u904d\u5386\u901a\u5f80\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a038.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u5305\u542b\u4e00\u4e2a\u521d\u59cb\u5316\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init\u7684\u51fd\u6570\uff0c\u90a3\u4e2a\u51fd\u6570\u5c06\u5728\u52a0\u8f7d\u6587\u4ef6\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u4efb\u4f55\u53c2\u6570\uff0c\u5e94\u8be5\u8fd4\u56devoid\u3002\u76ee\u524d\u6ca1\u6709\u529e\u6cd5\u5378\u8f7d\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u3002

\n
\n
\n
\n
\n
\n

38.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u5c06\u5b83\u4eec\u4f20\u5165\u51fd\u6570\u548c\u4ece\u51fd\u6570\u4f20\u51fa\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a038.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a038.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a038.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a038.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
texttext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

38.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy((void *) VARDATA(new_t), /* destination */\n           (void *) VARDATA_ANY(t), /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a038.10.8\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a039\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a058\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

\n
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\n
\n
\n
\n

38.10.4. \u7f16\u5199\u4ee3\u7801

\n
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\n
\n

\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a038.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a038.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

38.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 3.0 \u7248\u8d77\u9002\u7528\u3002

\n
\n
HP-UX
\n
\n

\u751f\u6210 PIC \u7684\u7cfb\u7edf\u7f16\u8bd1\u5668\u9009\u9879\u662f +z\u3002\u4f7f\u7528 GCC \u65f6\u5219\u662f -fPIC\u3002\u7528\u4e8e\u5171\u4eab\u5e93\u7684\u94fe\u63a5\u5668\u9009\u9879\u662f -b\u3002\u56e0\u6b64\uff1a

\n
cc +z -c foo.c\n
\n

\u6216\u8005\uff1a

\n
gcc -fPIC -c foo.c\n
\n

\u7136\u540e\uff1a

\n
ld -b -o foo.sl foo.o\n
\n

HP-UX \u4f7f\u7528 .sl \u4f5c\u4e3a\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff0c\u8fd9\u4e0e\u5927\u591a\u6570\u5176\u4ed6\u7cfb\u7edf\u4e0d\u540c\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a038.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

38.10.6. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u5b8f\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

38.10.7. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

38.10.8. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_INT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
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\n
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38.10.9. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

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\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a038.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

38.10.10. \u5171\u4eab\u5185\u5b58\u4e0e LWLocks

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLocks \u548c\u5171\u4eab\u5185\u5b58\u3002\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\u3002\u5171\u4eab\u5e93\u5e94\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\uff0c\u518d\u7531\u6b64\u94a9\u5b50\u9884\u7559 LWLocks \u6216\u5171\u4eab\u5185\u5b58\u3002\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u8c03\u7528\u5982\u4e0b\uff1a

\n
void RequestAddinShmemSpace(int size)\n
\n

\u5728 shmem_request_hook \u4e2d\u8c03\u7528\u3002

\n

\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u5728 shmem_request_hook \u4e2d\u8c03\u7528\u3002\u8fd9\u5c06\u786e\u4fdd\u5b58\u5728\u4e00\u4e2a\u540d\u4e3a tranche_name\u3001\u5305\u542b num_lwlocks \u4e2a LWLocks \u7684\u6570\u7ec4\u3002\u4f7f\u7528 GetNamedLWLockTranche \u83b7\u53d6\u8be5\u6570\u7ec4\u7684\u6307\u9488\u3002

\n

PostgreSQL \u6e90\u7801\u6811\u7684 contrib/pg_stat_statements/pg_stat_statements.c \u4e2d\u63d0\u4f9b\u4e86 shmem_request_hook \u793a\u4f8b\u3002

\n

\u4e3a\u907f\u514d\u7ade\u6001\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u9644\u52a0\u5230\u5176\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u5e76\u8fdb\u884c\u521d\u59cb\u5316\u65f6\uff0c\u90fd\u5e94\u4f7f\u7528\u8f7b\u91cf\u7ea7\u9501 AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\n\nif (!ptr)\n{\n        bool    found;\n\n        LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\n        ptr = ShmemInitStruct(\"my struct name\", size, &found);\n        if (!found)\n        {\n                initialize contents of shmem area;\n                acquire any requested LWLocks using:\n                ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n        }\n        LWLockRelease(AddinShmemInitLock);\n}\n
\n
\n
\n
\n
\n
\n

38.10.11. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
", "manual_path": "/docs/15/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/15/xfunc-c.html", "method": "same-major semantic node", "sha256": "525a67d45851e1ac7a414aeb9e309bc6f6ccd6c93cc6c70954c06bdb0e5279bd", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/p[10]", "#XFUNC-C/div[10]/p[1]", "#XFUNC-C/div[10]/p[2]", "#XFUNC-C/div[10]/p[6]", "#XFUNC-C/div[10]/p[7]", "#XFUNC-C/div[10]/p[8]", "#XFUNC-C/div[11]/div[7]/p[1]", "#XFUNC-C/div[11]/div[8]/p[1]", "#XFUNC-C/div[11]/p[11]", "#XFUNC-C/div[11]/p[13]", "#XFUNC-C/div[11]/p[14]", "#XFUNC-C/div[11]/p[16]", "#XFUNC-C/div[11]/p[18]", "#XFUNC-C/div[11]/p[19]", "#XFUNC-C/div[11]/p[1]", "#XFUNC-C/div[11]/p[21]", "#XFUNC-C/div[11]/p[22]", "#XFUNC-C/div[11]/p[24]", "#XFUNC-C/div[11]/p[25]", "#XFUNC-C/div[11]/p[27]", "#XFUNC-C/div[11]/p[28]", "#XFUNC-C/div[11]/p[3]", "#XFUNC-C/div[11]/p[4]", "#XFUNC-C/div[11]/p[6]", "#XFUNC-C/div[11]/p[9]", "#XFUNC-C/div[12]/div[19]/p[1]", "#XFUNC-C/div[12]/p[10]", "#XFUNC-C/div[12]/p[12]", "#XFUNC-C/div[12]/p[13]", "#XFUNC-C/div[12]/p[15]", "#XFUNC-C/div[12]/p[20]", "#XFUNC-C/div[12]/p[22]", "#XFUNC-C/div[12]/p[24]", "#XFUNC-C/div[12]/p[26]", "#XFUNC-C/div[12]/p[28]", "#XFUNC-C/div[12]/p[2]", "#XFUNC-C/div[12]/p[3]", "#XFUNC-C/div[12]/p[4]", "#XFUNC-C/div[12]/p[6]", "#XFUNC-C/div[12]/p[8]", "#XFUNC-C/div[13]/p[1]", "#XFUNC-C/div[13]/p[2]", "#XFUNC-C/div[13]/p[4]", "#XFUNC-C/div[13]/p[6]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[15]/p[2]", "#XFUNC-C/div[15]/p[4]", "#XFUNC-C/div[1]/dl[0]/dt[0]", "#XFUNC-C/div[1]/dl[0]/dt[10]", "#XFUNC-C/div[1]/dl[0]/dt[1]", "#XFUNC-C/div[1]/dl[0]/dt[2]", "#XFUNC-C/div[1]/dl[0]/dt[3]", "#XFUNC-C/div[1]/dl[0]/dt[4]", "#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[11]", "#XFUNC-C/div[5]/p[13]", "#XFUNC-C/div[5]/p[16]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[0]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[3]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[12]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[14]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[13]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", 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38.10.\u00a0C \u8bed\u8a00\u51fd\u6570

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\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

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\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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38.10.1. \u52a8\u6001\u8f7d\u5165

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\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u904d\u5386\u901a\u5f80\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a038.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u5305\u542b\u4e00\u4e2a\u521d\u59cb\u5316\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init\u7684\u51fd\u6570\uff0c\u90a3\u4e2a\u51fd\u6570\u5c06\u5728\u52a0\u8f7d\u6587\u4ef6\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u4efb\u4f55\u53c2\u6570\uff0c\u5e94\u8be5\u8fd4\u56devoid\u3002\u76ee\u524d\u6ca1\u6709\u529e\u6cd5\u5378\u8f7d\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u3002

\n
\n
\n
\n
\n
\n

38.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u5c06\u5b83\u4eec\u4f20\u5165\u51fd\u6570\u548c\u4ece\u51fd\u6570\u4f20\u51fa\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a038.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a038.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a038.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a038.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
\u6587\u672ctext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

38.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n#include \"varatt.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy(VARDATA(new_t),          /* destination */\n           VARDATA_ANY(t),          /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a038.10.8\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a039\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a058\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

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38.10.4. \u7f16\u5199\u4ee3\u7801

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\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

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    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a038.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a038.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

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    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

38.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 3.0 \u7248\u8d77\u9002\u7528\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a038.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

38.10.6. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u51fd\u6570\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

38.10.7. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

38.10.8. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_INT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

38.10.9. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a038.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

38.10.10. \u5171\u4eab\u5185\u5b58\u4e0e LWLocks

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLocks \u548c\u5171\u4eab\u5185\u5b58\u3002\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\u3002\u5171\u4eab\u5e93\u5e94\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\uff0c\u518d\u7531\u6b64\u94a9\u5b50\u9884\u7559 LWLocks \u6216\u5171\u4eab\u5185\u5b58\u3002\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u8c03\u7528\u5982\u4e0b\uff1a

\n
void RequestAddinShmemSpace(int size)\n
\n

\u5728 shmem_request_hook \u4e2d\u8c03\u7528\u3002

\n

\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u5728 shmem_request_hook \u4e2d\u8c03\u7528\u3002\u8fd9\u5c06\u786e\u4fdd\u5b58\u5728\u4e00\u4e2a\u540d\u4e3a tranche_name\u3001\u5305\u542b num_lwlocks \u4e2a LWLocks \u7684\u6570\u7ec4\u3002\u4f7f\u7528 GetNamedLWLockTranche \u83b7\u53d6\u8be5\u6570\u7ec4\u7684\u6307\u9488\u3002

\n

PostgreSQL \u6e90\u7801\u6811\u7684 contrib/pg_stat_statements/pg_stat_statements.c \u4e2d\u63d0\u4f9b\u4e86 shmem_request_hook \u793a\u4f8b\u3002

\n

\u4e3a\u907f\u514d\u7ade\u6001\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u9644\u52a0\u5230\u5176\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u5e76\u8fdb\u884c\u521d\u59cb\u5316\u65f6\uff0c\u90fd\u5e94\u4f7f\u7528\u8f7b\u91cf\u7ea7\u9501 AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\n\nif (!ptr)\n{\n        bool    found;\n\n        LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\n        ptr = ShmemInitStruct(\"my struct name\", size, &found);\n        if (!found)\n        {\n                initialize contents of shmem area;\n                acquire any requested LWLocks using:\n                ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n        }\n        LWLockRelease(AddinShmemInitLock);\n}\n
\n
\n
\n
\n
\n
\n

38.10.11. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
", "manual_path": "/docs/16/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/16/protocol-overview.html", "method": "same-major semantic node", "sha256": "44bc52e9e7ea6a128300584836e839d6a6b6b161cadff330571034de65b26ac1", "language": "zh", "matched_nodes": ["#PROTOCOL-OVERVIEW/div[9]/p[1]/span[2]/span[0]"]}, {"url": "/docs/16/xfunc-c.html", "method": "same-major semantic node", "sha256": "8809acadf9ad2b1e79b23f2446b430168f986eaa6d17e9b2e887266bb462299e", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/p[10]", "#XFUNC-C/div[10]/p[1]", "#XFUNC-C/div[10]/p[2]", "#XFUNC-C/div[10]/p[6]", "#XFUNC-C/div[10]/p[7]", "#XFUNC-C/div[10]/p[8]", "#XFUNC-C/div[11]/div[7]/p[1]", "#XFUNC-C/div[11]/div[8]/p[1]", "#XFUNC-C/div[11]/p[11]", "#XFUNC-C/div[11]/p[13]", "#XFUNC-C/div[11]/p[14]", "#XFUNC-C/div[11]/p[16]", "#XFUNC-C/div[11]/p[18]", "#XFUNC-C/div[11]/p[19]", "#XFUNC-C/div[11]/p[1]", "#XFUNC-C/div[11]/p[21]", "#XFUNC-C/div[11]/p[22]", "#XFUNC-C/div[11]/p[24]", "#XFUNC-C/div[11]/p[25]", "#XFUNC-C/div[11]/p[27]", "#XFUNC-C/div[11]/p[28]", "#XFUNC-C/div[11]/p[3]", "#XFUNC-C/div[11]/p[4]", "#XFUNC-C/div[11]/p[6]", "#XFUNC-C/div[11]/p[9]", "#XFUNC-C/div[12]/div[19]/p[1]", "#XFUNC-C/div[12]/p[10]", "#XFUNC-C/div[12]/p[12]", "#XFUNC-C/div[12]/p[13]", "#XFUNC-C/div[12]/p[15]", "#XFUNC-C/div[12]/p[20]", "#XFUNC-C/div[12]/p[22]", "#XFUNC-C/div[12]/p[24]", "#XFUNC-C/div[12]/p[26]", "#XFUNC-C/div[12]/p[28]", "#XFUNC-C/div[12]/p[2]", "#XFUNC-C/div[12]/p[3]", "#XFUNC-C/div[12]/p[4]", "#XFUNC-C/div[12]/p[6]", "#XFUNC-C/div[12]/p[8]", "#XFUNC-C/div[13]/p[1]", "#XFUNC-C/div[13]/p[2]", "#XFUNC-C/div[13]/p[4]", "#XFUNC-C/div[13]/p[6]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[15]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[15]/p[2]", "#XFUNC-C/div[15]/p[4]", "#XFUNC-C/div[1]/dl[0]/dt[0]", "#XFUNC-C/div[1]/dl[0]/dt[10]", "#XFUNC-C/div[1]/dl[0]/dt[1]", "#XFUNC-C/div[1]/dl[0]/dt[2]", "#XFUNC-C/div[1]/dl[0]/dt[3]", "#XFUNC-C/div[1]/dl[0]/dt[4]", "#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[11]", "#XFUNC-C/div[5]/p[13]", "#XFUNC-C/div[5]/p[16]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[0]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[3]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[12]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[14]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[5]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[7]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[9]/p[0]", "#XFUNC-C/div[9]/div[6]/h3[0]", "#XFUNC-C/div[9]/div[6]/p[1]", "#XFUNC-C/div[9]/p[1]", "#XFUNC-C/div[9]/p[2]", "#XFUNC-C/div[9]/p[4]", "#XFUNC-C/div[9]/p[7]", "#XFUNC-C/div[9]/p[8]", "#XFUNC-C/p[3]"]}], "language": "zh", "original_text": {"/versions/16/description/0": "dynamically-loaded C functions", "/versions/16/facts/0/label": "Kind", "/versions/16/facts/0/value": "Native function language", "/versions/16/facts/1/label": "Trusted", "/versions/16/facts/2/label": "Validator"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": 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\n
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\n

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\n

36.10.\u00a0C \u8bed\u8a00\u51fd\u6570

\n
\n
\n

\n
\n
\n
\n

\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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36.10.1. \u52a8\u6001\u8f7d\u5165

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\n

\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u904d\u5386\u901a\u5f80\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u5305\u542b\u4e00\u4e2a\u521d\u59cb\u5316\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init\u7684\u51fd\u6570\uff0c\u90a3\u4e2a\u51fd\u6570\u5c06\u5728\u52a0\u8f7d\u6587\u4ef6\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u4efb\u4f55\u53c2\u6570\uff0c\u5e94\u8be5\u8fd4\u56devoid\u3002\u76ee\u524d\u6ca1\u6709\u529e\u6cd5\u5378\u8f7d\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u3002

\n
\n
\n
\n
\n
\n

36.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u5c06\u5b83\u4eec\u4f20\u5165\u51fd\u6570\u548c\u4ece\u51fd\u6570\u4f20\u51fa\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a036.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a036.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a036.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a036.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
\u6587\u672ctext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n#include \"varatt.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy(VARDATA(new_t),          /* destination */\n           VARDATA_ANY(t),          /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a036.10.8\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a037\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a056\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

\n
\n
\n
\n
\n
\n

36.10.4. \u7f16\u5199\u4ee3\u7801

\n
\n
\n
\n

\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a036.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

36.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 13.0 \u8d77\u9002\u7528\uff1b\u66f4\u65e9\u7248\u672c\u4f7f\u7528\u7684\u662f gcc \u7f16\u8bd1\u5668\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

36.10.6. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u51fd\u6570\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

36.10.7. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.8. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_INT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
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\n
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36.10.9. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

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\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a036.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

36.10.10. \u5171\u4eab\u5185\u5b58

\n
\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.10.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

\n
\n
\n

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u3002\u4e3a\u6b64\uff0c\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\uff0c\u5e76\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\u3002\u6b64\u94a9\u5b50\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559\u5171\u4eab\u5185\u5b58\uff1a

\n
void RequestAddinShmemSpace(Size size)\n
\n

\u6765\u9884\u7559\u5171\u4eab\u5185\u5b58\u3002\u6bcf\u4e2a\u540e\u7aef\u90fd\u5e94\u5f53\u901a\u8fc7\u8c03\u7528\uff1a

\n
void *ShmemInitStruct(const char *name, Size size, bool *foundPtr)\n
\n

\u6765\u83b7\u53d6\u6307\u5411\u8fd9\u5757\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u6307\u9488\u3002\u5982\u679c\u8be5\u51fd\u6570\u628a foundPtr \u8bbe\u4e3a false\uff0c\u8c03\u7528\u8005\u5c31\u5e94\u521d\u59cb\u5316\u8fd9\u5757\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u5185\u5bb9\uff1b\u5982\u679c foundPtr \u4e3a true\uff0c\u8bf4\u660e\u8be5\u5171\u4eab\u5185\u5b58\u5df2\u7ecf\u7531\u5176\u4ed6\u540e\u7aef\u521d\u59cb\u5316\u8fc7\uff0c\u8c03\u7528\u8005\u65e0\u9700\u518d\u505a\u521d\u59cb\u5316\u3002

\n

\u4e3a\u907f\u514d\u7ade\u4e89\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u521d\u59cb\u5316\u5176\u5171\u4eab\u5185\u5b58\u5206\u914d\u65f6\u90fd\u5e94\u4f7f\u7528 LWLock AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\nbool        found;\n\nLWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\nptr = ShmemInitStruct(\"my struct name\", size, &found);\nif (!found)\n{\n    ... initialize contents of shared memory ...\n    ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n}\nLWLockRelease(AddinShmemInitLock);\n
\n

shmem_startup_hook \u4e3a\u521d\u59cb\u5316\u4ee3\u7801\u63d0\u4f9b\u4e86\u4e00\u4e2a\u65b9\u4fbf\u7684\u4f4d\u7f6e\uff0c\u4f46\u5e76\u4e0d\u5f3a\u5236\u8981\u6c42\u6240\u6709\u8fd9\u7c7b\u4ee3\u7801\u90fd\u653e\u5728\u8fd9\u4e2a\u94a9\u5b50\u4e2d\u3002\u5728 Windows \u4e0a\uff08\u4ee5\u53ca\u4efb\u4f55\u5b9a\u4e49\u4e86 EXEC_BACKEND \u7684\u5e73\u53f0\u4e0a\uff09\uff0c\u6bcf\u4e2a\u540e\u7aef\u90fd\u4f1a\u5728\u9644\u52a0\u5230\u5171\u4eab\u5185\u5b58\u540e\u4e0d\u4e45\u6267\u884c\u5df2\u6ce8\u518c\u7684 shmem_startup_hook\uff0c\u56e0\u6b64\u63d2\u4ef6\u5728\u8be5\u94a9\u5b50\u4e2d\u4ecd\u5e94\u50cf\u4e0a\u4f8b\u90a3\u6837\u83b7\u53d6 AddinShmemInitLock\u3002\u5728\u5176\u4ed6\u5e73\u53f0\u4e0a\uff0c\u53ea\u6709 postmaster \u8fdb\u7a0b\u4f1a\u6267\u884c shmem_startup_hook\uff0c\u6bcf\u4e2a\u540e\u7aef\u4f1a\u81ea\u52a8\u7ee7\u627f\u8fd9\u4e9b\u5171\u4eab\u5185\u5b58\u6307\u9488\u3002

\n

shmem_request_hook \u4e0e shmem_startup_hook \u7684\u4e00\u4e2a\u5b8c\u6574\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_stat_statements/pg_stat_statements.c\u3002

\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.10.2.\u00a0\u542f\u52a8\u540e\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

\n
\n
\n

\n
\n
\n
\n

\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u4e4b\u540e\uff0c\u5e76\u4e14\u65e0\u9700\u501f\u52a9 shmem_request_hook \u6765\u5b8c\u6210\u3002\u4e3a\u6b64\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8be5\u5171\u4eab\u5185\u5b58\u7684\u540e\u7aef\u90fd\u5e94\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u83b7\u53d6\u4e00\u4e2a\u6307\u9488\uff1a

\n
void *GetNamedDSMSegment(const char *name, size_t size,\n                         void (*init_callback) (void *ptr),\n                         bool *found)\n
\n

\u5982\u679c\u7ed9\u5b9a\u540d\u79f0\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u5c1a\u4e0d\u5b58\u5728\uff0c\u8be5\u51fd\u6570\u4f1a\u5206\u914d\u8be5\u6bb5\uff0c\u5e76\u4f7f\u7528\u63d0\u4f9b\u7684 init_callback \u56de\u8c03\u51fd\u6570\u5bf9\u5176\u8fdb\u884c\u521d\u59cb\u5316\u3002\u5982\u679c\u8be5\u6bb5\u5df2\u7ecf\u7531\u53e6\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8fc7\uff0c\u8be5\u51fd\u6570\u5c31\u53ea\u4f1a\u628a\u73b0\u6709\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u9644\u52a0\u5230\u5f53\u524d\u540e\u7aef\u3002

\n

\u4e0e\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559\u7684\u5171\u4eab\u5185\u5b58\u4e0d\u540c\uff0c\u4f7f\u7528 GetNamedDSMSegment \u9884\u7559\u5171\u4eab\u5185\u5b58\u65f6\uff0c\u65e0\u9700\u83b7\u53d6 AddinShmemInitLock\uff0c\u4e5f\u65e0\u9700\u91c7\u53d6\u5176\u4ed6\u63aa\u65bd\u907f\u514d\u7ade\u6001\u6761\u4ef6\u3002\u6b64\u51fd\u6570\u4fdd\u8bc1\u4ec5\u7531\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8be5\u6bb5\uff0c\u5176\u4ed6\u6240\u6709\u540e\u7aef\u83b7\u5f97\u7684\u90fd\u662f\u6307\u5411\u5df2\u5b8c\u5168\u5206\u914d\u5e76\u521d\u59cb\u5316\u7684\u6bb5\u7684\u6307\u9488\u3002

\n

GetNamedDSMSegment \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/test_dsm_registry/test_dsm_registry.c\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n
\n
\n
\n
\n
\n
\n

36.10.11. \u8f7b\u91cf\u7ea7\u9501\uff08LWLocks\uff09

\n
\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.11.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42 LWLocks

\n
\n
\n

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLocks\u3002\u4e0e\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u4e00\u6837\uff0c\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\uff0c\u5e76\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\u3002\u6b64\u94a9\u5b50\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8fd9\u786e\u4fdd\u5b58\u5728\u4e00\u4e2a\u540d\u4e3a tranche_name\u3001\u5305\u542b num_lwlocks \u4e2a LWLocks \u7684\u6570\u7ec4\u3002\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u53d6\u5f97\u8be5\u6570\u7ec4\u7684\u6307\u9488\uff1a

\n
LWLockPadded *GetNamedLWLockTranche(const char *tranche_name)\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.11.2.\u00a0\u542f\u52a8\u540e\u8bf7\u6c42 LWLocks

\n
\n
\n

\n
\n
\n
\n

\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u83b7\u53d6 LWLocks \u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u540e\u8fdb\u884c\uff0c\u4e5f\u65e0\u9700\u501f\u52a9 shmem_request_hook\u3002\u4e3a\u6b64\uff0c\u9996\u5148\u901a\u8fc7\u8c03\u7528\u4e0b\u9762\u7684\u51fd\u6570\u5206\u914d\u4e00\u4e2a tranche_id\uff1a

\n
int LWLockNewTrancheId(void)\n
\n

\u63a5\u4e0b\u6765\uff0c\u521d\u59cb\u5316\u6bcf\u4e2a LWLock\uff0c\u5e76\u628a\u65b0\u7684 tranche_id \u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\uff1a

\n
void LWLockInitialize(LWLock *lock, int tranche_id)\n
\n

\u4e0e\u5171\u4eab\u5185\u5b58\u7c7b\u4f3c\uff0c\u6bcf\u4e2a\u540e\u7aef\u90fd\u5e94\u786e\u4fdd\u53ea\u6709\u4e00\u4e2a\u8fdb\u7a0b\u4f1a\u5206\u914d\u65b0\u7684 tranche_id \u5e76\u521d\u59cb\u5316\u6bcf\u4e00\u4e2a\u65b0\u7684 LWLock\u3002\u4e00\u79cd\u505a\u6cd5\u662f\u4ec5\u5728\u6301\u6709 AddinShmemInitLock \u72ec\u5360\u9501\u7684\u5171\u4eab\u5185\u5b58\u521d\u59cb\u5316\u4ee3\u7801\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u3002\u5982\u679c\u4f7f\u7528 GetNamedDSMSegment\uff0c\u90a3\u4e48\u5728 init_callback \u56de\u8c03\u51fd\u6570\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u5c31\u8db3\u4ee5\u907f\u514d\u7ade\u4e89\u6761\u4ef6\u3002

\n

\u6700\u540e\uff0c\u6bcf\u4e2a\u4f7f\u7528\u8be5 tranche_id \u7684\u540e\u7aef\u90fd\u5e94\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u628a\u5b83\u4e0e\u4e00\u4e2a tranche_name \u5173\u8054\u8d77\u6765\uff1a

\n
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)\n
\n

LWLockNewTrancheId\u3001LWLockInitialize \u548c LWLockRegisterTranche \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_prewarm/autoprewarm.c\u3002

\n
\n
\n
\n
\n
\n
\n

36.10.12. \u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6

\n
\n
\n
\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u5728\u7b49\u5f85\u4e8b\u4ef6\u7c7b\u578b Extension \u4e0b\u5b9a\u4e49\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\uff1a

\n
uint32 WaitEventExtensionNew(const char *wait_event_name)\n
\n

\u8be5\u7b49\u5f85\u4e8b\u4ef6\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u9762\u5411\u7528\u6237\u7684\u81ea\u5b9a\u4e49\u5b57\u7b26\u4e32\u3002\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/worker_spi\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n

\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\u53ef\u4ee5\u5728 pg_stat_activity \u4e2d\u67e5\u770b\uff1a

\n
=# SELECT wait_event_type, wait_event FROM pg_stat_activity\n     WHERE backend_type ~ 'worker_spi';\n wait_event_type |  wait_event\n-----------------+---------------\n Extension       | WorkerSpiMain\n(1 row)\n
\n
\n
\n
\n
\n
\n

36.10.13. \u6ce8\u5165\u70b9

\n
\n
\n
\n

\u7ed9\u5b9a\u540d\u79f0 name \u7684\u6ce8\u5165\u70b9\u53ef\u901a\u8fc7\u4ee5\u4e0b\u5b8f\u58f0\u660e\uff1a

\n
INJECTION_POINT(name);\n
\n

\u670d\u52a1\u5668\u4ee3\u7801\u4e2d\u5df2\u7ecf\u5728\u82e5\u5e72\u5173\u952e\u4f4d\u7f6e\u58f0\u660e\u4e86\u6ce8\u5165\u70b9\u3002\u65b0\u589e\u6ce8\u5165\u70b9\u540e\uff0c\u9700\u8981\u91cd\u65b0\u7f16\u8bd1\u4ee3\u7801\uff0c\u624d\u80fd\u8ba9\u8be5\u6ce8\u5165\u70b9\u51fa\u73b0\u5728\u4e8c\u8fdb\u5236\u6587\u4ef6\u4e2d\u3002\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u4e5f\u53ef\u4ee5\u4f7f\u7528\u540c\u4e00\u4e2a\u5b8f\u5728\u81ea\u5df1\u7684\u4ee3\u7801\u4e2d\u58f0\u660e\u6ce8\u5165\u70b9\u3002\u6ce8\u5165\u70b9\u540d\u79f0\u5e94\u4f7f\u7528\u5c0f\u5199\u5b57\u6bcd\uff0c\u5e76\u7528\u8fde\u5b57\u7b26\u5206\u9694\u5404\u4e2a\u672f\u8bed\u3002

\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u4e3a\u4e00\u4e2a\u5df2\u7ecf\u58f0\u660e\u597d\u7684\u6ce8\u5165\u70b9\u9644\u52a0\u56de\u8c03\uff1a

\n
extern void InjectionPointAttach(const char *name,\n                                 const char *library,\n                                 const char *function,\n                                 const void *private_data,\n                                 int private_data_size);\n
\n

name \u662f\u6ce8\u5165\u70b9\u7684\u540d\u79f0\uff1b\u6267\u884c\u5230\u8fbe\u6b64\u6ce8\u5165\u70b9\u65f6\uff0c\u5c06\u6267\u884c\u4ece library \u52a0\u8f7d\u7684\u51fd\u6570\u3002private_data \u662f\u4e00\u5757\u5927\u5c0f\u4e3a private_data_size \u7684\u79c1\u6709\u6570\u636e\u533a\u57df\uff0c\u5728\u6267\u884c\u56de\u8c03\u65f6\u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\u3002

\n

\u4e0b\u9762\u662f\u4e00\u4e2a InjectionPointCallback \u7684\u793a\u4f8b\uff1a

\n
static void\ncustom_injection_callback(const char *name, const void *private_data)\n{\n    uint32 wait_event_info = WaitEventInjectionPointNew(name);\n\n    pgstat_report_wait_start(wait_event_info);\n    elog(NOTICE, \"%s: executed custom callback\", name);\n    pgstat_report_wait_end();\n}\n
\n

\u8fd9\u4e2a\u56de\u8c03\u4f1a\u4ee5 NOTICE \u7ea7\u522b\u5411\u670d\u52a1\u5668\u9519\u8bef\u65e5\u5fd7\u5199\u5165\u4e00\u6761\u6d88\u606f\uff0c\u4f46\u56de\u8c03\u5b8c\u5168\u53ef\u4ee5\u5b9e\u73b0\u66f4\u590d\u6742\u7684\u903b\u8f91\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e5f\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u89e3\u9664\u4e00\u4e2a\u6ce8\u5165\u70b9\uff1a

\n
extern bool InjectionPointDetach(const char *name);\n
\n

\u6210\u529f\u65f6\u8fd4\u56de true\uff0c\u5426\u5219\u8fd4\u56de false\u3002

\n

\u4e00\u4e2a\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u7684\u56de\u8c03\u4f1a\u5728\u6240\u6709\u540e\u7aef\u4e2d\u751f\u6548\uff0c\u5305\u62ec\u5728\u8c03\u7528 InjectionPointAttach \u4e4b\u540e\u624d\u542f\u52a8\u7684\u540e\u7aef\u3002\u5b83\u4f1a\u4e00\u76f4\u4fdd\u6301\u9644\u52a0\u72b6\u6001\uff0c\u76f4\u5230\u670d\u52a1\u5668\u505c\u6b62\uff0c\u6216\u8005\u901a\u8fc7 InjectionPointDetach \u5c06\u5176\u89e3\u9664\u3002

\n

\u76f8\u5173\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 src/test/modules/injection_points\u3002

\n

\u8981\u542f\u7528\u6ce8\u5165\u70b9\uff0c\u4f7f\u7528 configure \u65f6\u9700\u6307\u5b9a --enable-injection-points\uff0c\u4f7f\u7528 Meson \u65f6\u9700\u6307\u5b9a -Dinjection_points=true\u3002

\n
\n
\n
\n
\n
\n

36.10.14. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
", "manual_path": "/docs/17/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/17/protocol-overview.html", "method": "same-major semantic node", "sha256": "de94711d992bef74aad52fe8a723d81aa9b37a606d96b711bf9faa999a7bb3f5", "language": "zh", "matched_nodes": ["#PROTOCOL-OVERVIEW/div[9]/p[1]/span[2]/span[0]"]}, {"url": "/docs/17/xfunc-c.html", "method": "same-major semantic node", "sha256": "990e09637f0fb7a154eb0f5e8cb7b319a7603214d08975bd973130527b705f1f", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/p[10]", "#XFUNC-C/div[10]/p[1]", "#XFUNC-C/div[10]/p[2]", "#XFUNC-C/div[10]/p[6]", "#XFUNC-C/div[10]/p[7]", "#XFUNC-C/div[10]/p[8]", "#XFUNC-C/div[11]/div[7]/p[1]", "#XFUNC-C/div[11]/div[8]/p[1]", "#XFUNC-C/div[11]/p[11]", "#XFUNC-C/div[11]/p[13]", "#XFUNC-C/div[11]/p[14]", "#XFUNC-C/div[11]/p[16]", "#XFUNC-C/div[11]/p[18]", "#XFUNC-C/div[11]/p[19]", "#XFUNC-C/div[11]/p[1]", "#XFUNC-C/div[11]/p[21]", "#XFUNC-C/div[11]/p[22]", "#XFUNC-C/div[11]/p[24]", "#XFUNC-C/div[11]/p[25]", "#XFUNC-C/div[11]/p[27]", "#XFUNC-C/div[11]/p[28]", "#XFUNC-C/div[11]/p[3]", "#XFUNC-C/div[11]/p[4]", "#XFUNC-C/div[11]/p[6]", "#XFUNC-C/div[11]/p[9]", "#XFUNC-C/div[12]/div[19]/p[1]", "#XFUNC-C/div[12]/p[10]", "#XFUNC-C/div[12]/p[12]", "#XFUNC-C/div[12]/p[13]", "#XFUNC-C/div[12]/p[15]", "#XFUNC-C/div[12]/p[20]", "#XFUNC-C/div[12]/p[22]", "#XFUNC-C/div[12]/p[24]", "#XFUNC-C/div[12]/p[26]", "#XFUNC-C/div[12]/p[28]", "#XFUNC-C/div[12]/p[2]", "#XFUNC-C/div[12]/p[3]", "#XFUNC-C/div[12]/p[4]", "#XFUNC-C/div[12]/p[6]", "#XFUNC-C/div[12]/p[8]", "#XFUNC-C/div[13]/p[1]", "#XFUNC-C/div[13]/p[2]", "#XFUNC-C/div[13]/p[4]", "#XFUNC-C/div[13]/p[6]", "#XFUNC-C/div[14]/div[1]/div[0]", "#XFUNC-C/div[14]/div[1]/p[3]", "#XFUNC-C/div[14]/div[1]/p[5]", "#XFUNC-C/div[14]/div[1]/p[6]", "#XFUNC-C/div[14]/div[1]/p[8]", "#XFUNC-C/div[14]/div[1]/p[9]", "#XFUNC-C/div[14]/div[2]/div[0]", "#XFUNC-C/div[14]/div[2]/p[1]", "#XFUNC-C/div[14]/div[2]/p[3]", "#XFUNC-C/div[14]/div[2]/p[5]", "#XFUNC-C/div[15]/div[1]/div[0]", "#XFUNC-C/div[15]/div[2]/div[0]", "#XFUNC-C/div[15]/div[2]/p[1]", "#XFUNC-C/div[15]/div[2]/p[3]", "#XFUNC-C/div[15]/div[2]/p[5]", "#XFUNC-C/div[15]/div[2]/p[6]", "#XFUNC-C/div[15]/div[2]/p[8]", "#XFUNC-C/div[16]/p[1]", "#XFUNC-C/div[16]/p[3]", "#XFUNC-C/div[16]/p[4]", "#XFUNC-C/div[17]/p[10]", "#XFUNC-C/div[17]/p[12]", "#XFUNC-C/div[17]/p[13]", "#XFUNC-C/div[17]/p[14]", "#XFUNC-C/div[17]/p[1]", "#XFUNC-C/div[17]/p[3]", "#XFUNC-C/div[17]/p[4]", "#XFUNC-C/div[17]/p[7]", "#XFUNC-C/div[17]/p[9]", "#XFUNC-C/div[18]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[18]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[18]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[18]/p[2]", "#XFUNC-C/div[18]/p[4]", "#XFUNC-C/div[1]/dl[0]/dt[0]", "#XFUNC-C/div[1]/dl[0]/dt[11]", "#XFUNC-C/div[1]/dl[0]/dt[12]", "#XFUNC-C/div[1]/dl[0]/dt[13]", "#XFUNC-C/div[1]/dl[0]/dt[1]", "#XFUNC-C/div[1]/dl[0]/dt[2]", "#XFUNC-C/div[1]/dl[0]/dt[3]", "#XFUNC-C/div[1]/dl[0]/dt[4]", "#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[11]", "#XFUNC-C/div[5]/p[13]", "#XFUNC-C/div[5]/p[16]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[0]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[3]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[12]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[14]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[5]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[7]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[9]/p[0]", "#XFUNC-C/div[9]/div[6]/h3[0]", "#XFUNC-C/div[9]/div[6]/p[1]", "#XFUNC-C/div[9]/p[1]", "#XFUNC-C/div[9]/p[2]", "#XFUNC-C/div[9]/p[4]", "#XFUNC-C/div[9]/p[7]", "#XFUNC-C/div[9]/p[8]", "#XFUNC-C/p[3]"]}], "language": "zh", "original_text": {"/versions/17/description/0": "dynamically-loaded C functions", "/versions/17/facts/0/label": "Kind", "/versions/17/facts/0/value": "Native function language", "/versions/17/facts/1/label": "Trusted", "/versions/17/facts/2/label": "Validator"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "2c3890fb4f955e74b41376d7aa8a6d9ec77b0b73f577f6ef0c1f7ed78f388cb1"}, "comparison_data": {"kind": "Native function language", "handler": "", "trusted": "f", "validator": "fmgr_c_validator"}, "comparison_hash": "e8a219c1a26602affef41a21da26d099cf721ba42739cb7b056898c9e2d6fbe6", "manual_language": "zh"}, "18": {"facts": [{"label": "\u79cd\u7c7b", "value": "\u539f\u751f\u51fd\u6570\u8bed\u8a00"}, {"label": "\u53ef\u4fe1", "value": "f"}, {"label": "\u6821\u9a8c\u51fd\u6570", "value": "fmgr_c_validator"}], "tables": [], "aliases": [], "catalog": {"oid": "13", "descr": "dynamically-loaded C functions", "lanacl": "_null_", "lanispl": "f", "lanname": "c", "lanowner": "POSTGRES", "laninline": "0", "oid_symbol": "ClanguageId", "lanpltrusted": "f", "lanvalidator": "fmgr_c_validator", "lanplcallfoid": "0"}, "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "18.6", "major": "18", "channel": "stable", "revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f", "source_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f", "catalog_fingerprint": "65c93d6048ef30e61023a84f9680fa6a92b1c383b7eb226741170077eb078502"}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "Matching PostgreSQL source archive", "sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://pg.center/docs/18/xfunc-c.html", "path": "xfunc-c.html", "label": "PostgreSQL 18 English manual", "sha256": "d60592edc11f3240b19cecee91523a9a31f1caf68809fa7a39376360d957d68b", "language": "en", "original_url": "/docs/18/xfunc-c.html"}], "sections": [], "signature": "", "attributes": {"kind": "Native function language", "handler": "", "trusted": "f", "validator": "fmgr_c_validator"}, "description": ["\u52a8\u6001\u52a0\u8f7d\u7684 C \u51fd\u6570"], "manual_html": "
\n
\n
\n
\n

\n
\n
\n

36.10.\u00a0C \u8bed\u8a00\u51fd\u6570

\n
\n
\n

\n
\n
\n
\n

\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

\n
\n
\n
\n
\n

36.10.1. \u52a8\u6001\u8f7d\u5165

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\n
\n
\n

\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u904d\u5386\u901a\u5f80\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u6216\u8005

\n
PG_MODULE_MAGIC_EXT(parameters);\n
\n

PG_MODULE_MAGIC_EXT \u8fd9\u79cd\u5f62\u5f0f\u5141\u8bb8\u4e3a\u6a21\u5757\u6307\u5b9a\u9644\u52a0\u4fe1\u606f\uff1b\u76ee\u524d\u53ef\u4ee5\u6dfb\u52a0\u540d\u79f0\u548c/\u6216\u7248\u672c\u5b57\u7b26\u4e32\u3002\uff08\u5c06\u6765\u53ef\u80fd\u5141\u8bb8\u66f4\u591a\u5b57\u6bb5\u3002\uff09\u53ef\u4ee5\u5199\u6210\u8fd9\u6837\uff1a

\n
PG_MODULE_MAGIC_EXT(\n    .name = \"my_module_name\",\n    .version = \"1.2.3\"\n);\n
\n

\u4e4b\u540e\uff0c\u540d\u79f0\u548c\u7248\u672c\u53ef\u4ee5\u901a\u8fc7 pg_get_loaded_modules() \u51fd\u6570\u67e5\u770b\u3002\u7248\u672c\u5b57\u7b26\u4e32\u7684\u5177\u4f53\u542b\u4e49\u4e0d\u53d7 PostgreSQL \u9650\u5236\uff0c\u4f46\u5efa\u8bae\u91c7\u7528\u8bed\u4e49\u5316\u7248\u672c\u89c4\u5219\u3002

\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u5305\u542b\u4e00\u4e2a\u521d\u59cb\u5316\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init\u7684\u51fd\u6570\uff0c\u90a3\u4e2a\u51fd\u6570\u5c06\u5728\u52a0\u8f7d\u6587\u4ef6\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u4efb\u4f55\u53c2\u6570\uff0c\u5e94\u8be5\u8fd4\u56devoid\u3002\u76ee\u524d\u6ca1\u6709\u529e\u6cd5\u5378\u8f7d\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u3002

\n
\n
\n
\n
\n
\n

36.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u5c06\u5b83\u4eec\u4f20\u5165\u51fd\u6570\u548c\u4ece\u51fd\u6570\u4f20\u51fa\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a036.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a036.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a036.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a036.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
\u6587\u672ctext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u8981\u8c03\u7528\u53e6\u4e00\u4e2a\u7248\u672c-1 \u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528 DirectFunctionCalln(func, arg1, ..., argn)\u3002\u8fd9\u5728\u4f60\u60f3\u8c03\u7528\u6807\u51c6\u5185\u90e8\u5e93\u4e2d\u5b9a\u4e49\u7684\u51fd\u6570\u65f6\u5c24\u5176\u6709\u7528\uff0c\u56e0\u4e3a\u5b83\u63d0\u4f9b\u4e86\u4e0e\u5176 SQL \u7b7e\u540d\u76f8\u4f3c\u7684\u63a5\u53e3\u3002

\n

\u8fd9\u4e9b\u4fbf\u5229\u51fd\u6570\u4ee5\u53ca\u7c7b\u4f3c\u51fd\u6570\u90fd\u53ef\u4ee5\u5728 fmgr.h \u4e2d\u627e\u5230\u3002DirectFunctionCalln \u7cfb\u5217\u628a C \u51fd\u6570\u540d\u4f5c\u4e3a\u5176\u7b2c\u4e00\u4e2a\u53c2\u6570\u3002\u53e6\u6709 OidFunctionCalln \u7b49\u4e00\u4e9b\u53d8\u4f53\uff0c\u5b83\u4eec\u63a5\u6536\u76ee\u6807\u51fd\u6570\u7684 OID\u3002\u6240\u6709\u8fd9\u4e9b\u51fd\u6570\u90fd\u8981\u6c42\u4ee5 Datum \u5f62\u5f0f\u63d0\u4f9b\u51fd\u6570\u53c2\u6570\uff0c\u8fd4\u56de\u503c\u4e5f\u540c\u6837\u662f Datum\u3002\u6ce8\u610f\uff0c\u4f7f\u7528\u8fd9\u4e9b\u4fbf\u5229\u51fd\u6570\u65f6\uff0c\u53c2\u6570\u548c\u7ed3\u679c\u90fd\u4e0d\u80fd\u4e3a NULL\u3002

\n

\u4f8b\u5982\uff0c\u8981\u5728 C \u4e2d\u8c03\u7528 starts_with(text, text)\uff0c\u4f60\u53ef\u4ee5\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\u67e5\u5230\u5b83\u7684 C \u5b9e\u73b0\u662f Datum text_starts_with(PG_FUNCTION_ARGS) \u51fd\u6570\u3002\u901a\u5e38\u4f60\u4f1a\u7528 DirectFunctionCall2(text_starts_with, ...) \u6765\u8c03\u7528\u5b83\u3002\u4e0d\u8fc7\uff0cstarts_with(text, text) \u9700\u8981\u6392\u5e8f\u89c4\u5219\u4fe1\u606f\uff0c\u56e0\u6b64\u5982\u679c\u8fd9\u6837\u8c03\u7528\uff0c\u4f1a\u56e0\u201c\u65e0\u6cd5\u786e\u5b9a\u5b57\u7b26\u4e32\u6bd4\u8f83\u8be5\u4f7f\u7528\u54ea\u4e00\u79cd\u6392\u5e8f\u89c4\u5219\u201d\u800c\u5931\u8d25\u3002\u4f60\u5fc5\u987b\u6539\u7528 DirectFunctionCall2Coll(text_starts_with, ...)\uff0c\u5e76\u63d0\u4f9b\u6240\u9700\u7684\u6392\u5e8f\u89c4\u5219\uff0c\u901a\u5e38\u5c31\u662f\u4ece PG_GET_COLLATION() \u4f20\u9012\u8fdb\u6765\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u6240\u793a\u3002

\n

fmgr.h \u8fd8\u63d0\u4f9b\u4e86\u4fbf\u4e8e\u5728 C \u7c7b\u578b\u548c Datum \u4e4b\u95f4\u8f6c\u6362\u7684\u5b8f\u3002\u4f8b\u5982\uff0c\u8981\u628a Datum \u8f6c\u6210 text*\uff0c\u53ef\u4ee5\u4f7f\u7528 DatumGetTextPP(X)\u3002\u867d\u7136\u67d0\u4e9b\u7c7b\u578b\u4e3a\u53cd\u5411\u8f6c\u6362\u63d0\u4f9b\u4e86\u540d\u4e3a TypeGetDatum(X) \u4e4b\u7c7b\u7684\u5b8f\uff0c\u4f46 text* \u6ca1\u6709\uff1b\u5bf9\u5b83\u800c\u8a00\uff0c\u76f4\u63a5\u4f7f\u7528\u901a\u7528\u5b8f PointerGetDatum(X) \u5373\u53ef\u3002\u5982\u679c\u4f60\u7684\u6269\u5c55\u5b9a\u4e49\u4e86\u989d\u5916\u7684\u7c7b\u578b\uff0c\u901a\u5e38\u4e5f\u5f88\u65b9\u4fbf\u4e3a\u8fd9\u4e9b\u7c7b\u578b\u5b9a\u4e49\u7c7b\u4f3c\u7684\u5b8f\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n#include \"varatt.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy(VARDATA(new_t),          /* destination */\n           VARDATA_ANY(t),          /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n/* A wrapper around starts_with(text, text) */\n\nPG_FUNCTION_INFO_V1(t_starts_with);\n\nDatum\nt_starts_with(PG_FUNCTION_ARGS)\n{\n    text       *t1 = PG_GETARG_TEXT_PP(0);\n    text       *t2 = PG_GETARG_TEXT_PP(1);\n    Oid         collid = PG_GET_COLLATION();\n    bool        result;\n\n    result = DatumGetBool(DirectFunctionCall2Coll(text_starts_with,\n                                                  collid,\n                                                  PointerGetDatum(t1),\n                                                  PointerGetDatum(t2)));\n    PG_RETURN_BOOL(result);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION t_starts_with(text, text) RETURNS boolean\n     AS 'DIRECTORY/funcs', 't_starts_with'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a036.10.9\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a037\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a057\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

\n
\n
\n
\n
\n
\n

36.10.4. \u7f16\u5199\u4ee3\u7801

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\n
\n
\n

\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a036.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

36.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 13.0 \u8d77\u9002\u7528\uff1b\u66f4\u65e9\u7248\u672c\u4f7f\u7528\u7684\u662f gcc \u7f16\u8bd1\u5668\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

36.10.6. \u670d\u52a1\u5668 API \u548c ABI \u7a33\u5b9a\u6027\u6307\u5357

\n
\n
\n
\n

\u672c\u8282\u5411\u6269\u5c55\u548c\u5176\u4ed6\u670d\u52a1\u5668\u63d2\u4ef6\u7684\u4f5c\u8005\u63d0\u4f9b\u6709\u5173 PostgreSQL \u670d\u52a1\u5668 API \u4e0e ABI \u7a33\u5b9a\u6027\u7684\u6307\u5bfc\u3002

\n
\n
\n
\n
\n

\n
\n
\n

36.10.6.1.\u00a0\u6982\u8ff0

\n
\n
\n

\n
\n
\n
\n

PostgreSQL \u670d\u52a1\u5668\u4e3a\u63d2\u4ef6\u63d0\u4f9b\u4e86\u591a\u4e2a\u8fb9\u754c\u6e05\u6670\u7684 API\uff0c\u4f8b\u5982\u672c\u7ae0\u4ecb\u7ecd\u7684\u51fd\u6570\u7ba1\u7406\u5668 fmgr\u3001SPI\uff08\u7b2c 45 \u7ae0\uff09\u4ee5\u53ca\u4e13\u4e3a\u6269\u5c55\u8bbe\u8ba1\u7684\u5404\u79cd\u94a9\u5b50\u3002\u8fd9\u4e9b\u63a5\u53e3\u7ecf\u8fc7\u8c28\u614e\u7ef4\u62a4\uff0c\u4ee5\u4fdd\u6301\u957f\u671f\u7a33\u5b9a\u6027\u548c\u517c\u5bb9\u6027\u3002\u4e0d\u8fc7\uff0c\u670d\u52a1\u5668\u4e2d\u5168\u90e8\u5168\u5c40\u51fd\u6570\u548c\u53d8\u91cf\u5b9e\u9645\u4e0a\u90fd\u6784\u6210\u4e86\u53ef\u516c\u5f00\u4f7f\u7528\u7684 API\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u5728\u8bbe\u8ba1\u65f6\u5e76\u672a\u8003\u8651\u53ef\u6269\u5c55\u6027\u548c\u957f\u671f\u7a33\u5b9a\u6027\u3002

\n

\u56e0\u6b64\uff0c\u867d\u7136\u4f7f\u7528\u8fd9\u4e9b\u63a5\u53e3\u662f\u5b8c\u5168\u5141\u8bb8\u7684\uff0c\u4f46\u8d8a\u662f\u504f\u79bb\u90a3\u4e9b\u4e45\u7ecf\u5b9e\u8df5\u8003\u9a8c\u7684\u8def\u5f84\uff0c\u5c06\u6765\u9047\u5230 API \u6216 ABI \u517c\u5bb9\u6027\u95ee\u9898\u7684\u53ef\u80fd\u6027\u5c31\u8d8a\u5927\u3002\u9f13\u52b1\u6269\u5c55\u4f5c\u8005\u53cd\u9988\u81ea\u5df1\u7684\u9700\u6c42\uff0c\u4ee5\u4fbf\u968f\u7740\u65f6\u95f4\u63a8\u79fb\u548c\u65b0\u7528\u6cd5\u7684\u51fa\u73b0\uff0c\u67d0\u4e9b\u63a5\u53e3\u80fd\u591f\u88ab\u89c6\u4e3a\u66f4\u7a33\u5b9a\uff0c\u6216\u8005\u53ef\u4ee5\u52a0\u5165\u65b0\u7684\u3001\u8bbe\u8ba1\u66f4\u5b8c\u5584\u7684\u63a5\u53e3\u3002

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36.10.6.2.\u00a0API \u517c\u5bb9\u6027

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\n

API\uff0c\u5373\u5e94\u7528\u7a0b\u5e8f\u7f16\u7a0b\u63a5\u53e3\uff0c\u662f\u7f16\u8bd1\u65f6\u4f7f\u7528\u7684\u63a5\u53e3\u3002

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36.10.6.2.1.\u00a0Major Versions
\n
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\u5728 PostgreSQL \u4e0d\u540c\u4e3b\u7248\u672c\u4e4b\u95f4\uff0c\u4e0d\u627f\u8bfa API \u517c\u5bb9\u6027\u3002\u56e0\u6b64\uff0c\u6269\u5c55\u4ee3\u7801\u53ef\u80fd\u9700\u8981\u4fee\u6539\u6e90\u4ee3\u7801\u624d\u80fd\u540c\u65f6\u652f\u6301\u591a\u4e2a\u4e3b\u7248\u672c\u3002\u8fd9\u7c7b\u5dee\u5f02\u901a\u5e38\u53ef\u4ee5\u901a\u8fc7\u9884\u5904\u7406\u5668\u6761\u4ef6\uff08\u4f8b\u5982 #if PG_VERSION_NUM >= 160000\uff09\u6765\u7ba1\u7406\u3002\u90a3\u4e9b\u4f7f\u7528\u4e86\u8fb9\u754c\u6e05\u6670\u63a5\u53e3\u4e4b\u5916\u80fd\u529b\u7684\u590d\u6742\u6269\u5c55\uff0c\u901a\u5e38\u6bcf\u4e2a\u670d\u52a1\u5668\u4e3b\u7248\u672c\u90fd\u9700\u8981\u505a\u5c11\u91cf\u8fd9\u7c7b\u4fee\u6539\u3002

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36.10.6.2.2.\u00a0Minor Versions
\n
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PostgreSQL \u4f1a\u5c3d\u529b\u907f\u514d\u5728\u5c0f\u7248\u672c\u53d1\u5e03\u4e2d\u7834\u574f\u670d\u52a1\u5668 API\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u80fd\u9488\u5bf9\u67d0\u4e2a\u5c0f\u7248\u672c\u7f16\u8bd1\u5e76\u6b63\u5e38\u5de5\u4f5c\u7684\u6269\u5c55\u4ee3\u7801\uff0c\u4e5f\u5e94\u5f53\u80fd\u591f\u9488\u5bf9\u540c\u4e00\u4e3b\u7248\u672c\u7684\u5176\u4ed6\u4efb\u610f\u5c0f\u7248\u672c\uff08\u65e0\u8bba\u8fc7\u53bb\u8fd8\u662f\u5c06\u6765\uff09\u7f16\u8bd1\u5e76\u6b63\u5e38\u5de5\u4f5c\u3002

\n

\u5982\u679c\u786e\u5b9e\u9700\u8981\u505a\u51fa\u53d8\u66f4\uff0c\u4e5f\u4f1a\u5728\u8003\u8651\u6269\u5c55\u9700\u6c42\u7684\u524d\u63d0\u4e0b\u8c28\u614e\u7ba1\u7406\u3002\u8fd9\u7c7b\u53d8\u66f4\u4f1a\u5728\u53d1\u5e03\u8bf4\u660e\uff08\u9644\u5f55\u00a0E\uff09\u4e2d\u8fdb\u884c\u8bf4\u660e\u3002

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36.10.6.3.\u00a0ABI \u517c\u5bb9\u6027

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ABI\uff0c\u5373\u5e94\u7528\u7a0b\u5e8f\u4e8c\u8fdb\u5236\u63a5\u53e3\uff0c\u662f\u8fd0\u884c\u65f6\u4f7f\u7528\u7684\u63a5\u53e3\u3002

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36.10.6.3.1.\u00a0Major Versions
\n
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\u4e0d\u540c\u4e3b\u7248\u672c\u7684\u670d\u52a1\u5668\u5728 ABI \u4e0a\u662f\u6709\u610f\u4e0d\u517c\u5bb9\u7684\u3002\u56e0\u6b64\uff0c\u4f7f\u7528\u670d\u52a1\u5668 API \u7684\u6269\u5c55\u5fc5\u987b\u9488\u5bf9\u6bcf\u4e00\u4e2a\u4e3b\u7248\u672c\u91cd\u65b0\u7f16\u8bd1\u3002\u5305\u542b PG_MODULE_MAGIC\uff08\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\uff09\u53ef\u4ee5\u786e\u4fdd\u9488\u5bf9\u67d0\u4e2a\u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u4ee3\u7801\u4f1a\u88ab\u5176\u4ed6\u4e3b\u7248\u672c\u62d2\u7edd\u3002

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36.10.6.3.2.\u00a0Minor Versions
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PostgreSQL \u4f1a\u5c3d\u529b\u907f\u514d\u5728\u5c0f\u7248\u672c\u53d1\u5e03\u4e2d\u7834\u574f\u670d\u52a1\u5668 ABI\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u9488\u5bf9\u4efb\u610f\u4e00\u4e2a\u5c0f\u7248\u672c\u7f16\u8bd1\u7684\u6269\u5c55\uff0c\u5e94\u5f53\u80fd\u4e0e\u540c\u4e00\u4e3b\u7248\u672c\u8fc7\u53bb\u6216\u5c06\u6765\u7684\u5176\u4ed6\u4efb\u610f\u5c0f\u7248\u672c\u4e00\u8d77\u5de5\u4f5c\u3002

\n

\u5982\u679c\u786e\u5b9e\u9700\u8981\u53d8\u66f4\uff0cPostgreSQL \u4f1a\u5c3d\u91cf\u9009\u62e9\u4fb5\u5165\u6027\u6700\u5c0f\u7684\u65b9\u5f0f\uff0c\u4f8b\u5982\u628a\u65b0\u5b57\u6bb5\u585e\u8fdb\u586b\u5145\u7a7a\u95f4\uff0c\u6216\u8005\u9644\u52a0\u5230\u7ed3\u6784\u4f53\u672b\u5c3e\u3002\u8fd9\u7c7b\u4fee\u6539\u901a\u5e38\u4e0d\u5e94\u5f71\u54cd\u6269\u5c55\uff0c\u9664\u975e\u6269\u5c55\u4f7f\u7528\u4e86\u975e\u5e38\u4e0d\u5bfb\u5e38\u7684\u4ee3\u7801\u6a21\u5f0f\u3002

\n

\u7136\u800c\uff0c\u5728\u6781\u5c11\u6570\u60c5\u51b5\u4e0b\uff0c\u5373\u4f7f\u662f\u8fd9\u79cd\u975e\u4fb5\u5165\u5f0f\u53d8\u66f4\u4e5f\u53ef\u80fd\u4e0d\u73b0\u5b9e\u751a\u81f3\u4e0d\u53ef\u80fd\u505a\u5230\u3002\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\u65f6\uff0c\u4e5f\u4f1a\u5728\u8003\u8651\u6269\u5c55\u9700\u6c42\u7684\u524d\u63d0\u4e0b\u8c28\u614e\u7ba1\u7406\u8be5\u53d8\u66f4\u3002\u8fd9\u7c7b\u53d8\u66f4\u540c\u6837\u4f1a\u8bb0\u5f55\u5728\u53d1\u5e03\u8bf4\u660e\uff08\u9644\u5f55\u00a0E\uff09\u4e2d\u3002

\n

\u4f46\u8bf7\u6ce8\u610f\uff0c\u670d\u52a1\u5668\u4e2d\u6709\u5f88\u591a\u90e8\u5206\u5e76\u4e0d\u662f\u4f5c\u4e3a\u53ef\u516c\u5f00\u4f7f\u7528\u7684 API \u6765\u8bbe\u8ba1\u548c\u7ef4\u62a4\u7684\uff08\u800c\u4e14\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u5176\u771f\u5b9e\u8fb9\u754c\u4e5f\u5e76\u4e0d\u6e05\u6670\uff09\u3002\u5982\u679c\u51fa\u73b0\u7d27\u6025\u9700\u6c42\uff0c\u5bf9\u8fd9\u4e9b\u90e8\u5206\u8fdb\u884c\u4fee\u6539\u65f6\uff0c\u81ea\u7136\u4f1a\u6bd4\u4fee\u6539\u90a3\u4e9b\u8fb9\u754c\u6e05\u695a\u4e14\u5e7f\u6cdb\u4f7f\u7528\u7684\u63a5\u53e3\u65f6\u66f4\u5c11\u8003\u8651\u6269\u5c55\u4ee3\u7801\u7684\u517c\u5bb9\u6027\u3002

\n

\u6b64\u5916\uff0c\u5728\u7f3a\u4e4f\u81ea\u52a8\u5316\u68c0\u6d4b\u8fd9\u7c7b\u53d8\u5316\u7684\u673a\u5236\u65f6\uff0c\u8fd9\u5e76\u4e0d\u80fd\u6784\u6210\u4e25\u683c\u4fdd\u8bc1\uff1b\u4e0d\u8fc7\u4ece\u5386\u53f2\u4e0a\u770b\uff0c\u8fd9\u79cd\u7834\u574f\u6027\u53d8\u5316\u6781\u4e3a\u7f55\u89c1\u3002

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36.10.7. \u590d\u5408\u7c7b\u578b\u53c2\u6570

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\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u51fd\u6570\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

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36.10.8. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
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\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.9. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_INT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

36.10.10. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a036.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

36.10.11. \u5171\u4eab\u5185\u5b58

\n
\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.11.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

\n
\n
\n

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u3002\u4e3a\u6b64\uff0c\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\uff0c\u5e76\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\u3002\u6b64\u94a9\u5b50\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559\u5171\u4eab\u5185\u5b58\uff1a

\n
void RequestAddinShmemSpace(Size size)\n
\n

\u6765\u9884\u7559\u5171\u4eab\u5185\u5b58\u3002\u6bcf\u4e2a\u540e\u7aef\u90fd\u5e94\u5f53\u901a\u8fc7\u8c03\u7528\uff1a

\n
void *ShmemInitStruct(const char *name, Size size, bool *foundPtr)\n
\n

\u6765\u83b7\u53d6\u6307\u5411\u8fd9\u5757\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u6307\u9488\u3002\u5982\u679c\u8be5\u51fd\u6570\u628a foundPtr \u8bbe\u4e3a false\uff0c\u8c03\u7528\u8005\u5c31\u5e94\u521d\u59cb\u5316\u8fd9\u5757\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u5185\u5bb9\uff1b\u5982\u679c foundPtr \u4e3a true\uff0c\u8bf4\u660e\u8be5\u5171\u4eab\u5185\u5b58\u5df2\u7ecf\u7531\u5176\u4ed6\u540e\u7aef\u521d\u59cb\u5316\u8fc7\uff0c\u8c03\u7528\u8005\u65e0\u9700\u518d\u505a\u521d\u59cb\u5316\u3002

\n

\u4e3a\u907f\u514d\u7ade\u4e89\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u521d\u59cb\u5316\u5176\u5171\u4eab\u5185\u5b58\u5206\u914d\u65f6\u90fd\u5e94\u4f7f\u7528 LWLock AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\nbool        found;\n\nLWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\nptr = ShmemInitStruct(\"my struct name\", size, &found);\nif (!found)\n{\n    ... initialize contents of shared memory ...\n    ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n}\nLWLockRelease(AddinShmemInitLock);\n
\n

shmem_startup_hook \u4e3a\u521d\u59cb\u5316\u4ee3\u7801\u63d0\u4f9b\u4e86\u4e00\u4e2a\u65b9\u4fbf\u7684\u4f4d\u7f6e\uff0c\u4f46\u5e76\u4e0d\u5f3a\u5236\u8981\u6c42\u6240\u6709\u8fd9\u7c7b\u4ee3\u7801\u90fd\u653e\u5728\u8fd9\u4e2a\u94a9\u5b50\u4e2d\u3002\u5728 Windows \u4e0a\uff08\u4ee5\u53ca\u4efb\u4f55\u5b9a\u4e49\u4e86 EXEC_BACKEND \u7684\u5e73\u53f0\u4e0a\uff09\uff0c\u6bcf\u4e2a\u540e\u7aef\u90fd\u4f1a\u5728\u9644\u52a0\u5230\u5171\u4eab\u5185\u5b58\u540e\u4e0d\u4e45\u6267\u884c\u5df2\u6ce8\u518c\u7684 shmem_startup_hook\uff0c\u56e0\u6b64\u63d2\u4ef6\u5728\u8be5\u94a9\u5b50\u4e2d\u4ecd\u5e94\u50cf\u4e0a\u4f8b\u90a3\u6837\u83b7\u53d6 AddinShmemInitLock\u3002\u5728\u5176\u4ed6\u5e73\u53f0\u4e0a\uff0c\u53ea\u6709 postmaster \u8fdb\u7a0b\u4f1a\u6267\u884c shmem_startup_hook\uff0c\u6bcf\u4e2a\u540e\u7aef\u4f1a\u81ea\u52a8\u7ee7\u627f\u8fd9\u4e9b\u5171\u4eab\u5185\u5b58\u6307\u9488\u3002

\n

shmem_request_hook \u4e0e shmem_startup_hook \u7684\u4e00\u4e2a\u5b8c\u6574\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_stat_statements/pg_stat_statements.c\u3002

\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.11.2.\u00a0\u542f\u52a8\u540e\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

\n
\n
\n

\n
\n
\n
\n

\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u4e4b\u540e\uff0c\u5e76\u4e14\u65e0\u9700\u501f\u52a9 shmem_request_hook \u6765\u5b8c\u6210\u3002\u4e3a\u6b64\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8be5\u5171\u4eab\u5185\u5b58\u7684\u540e\u7aef\u90fd\u5e94\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u83b7\u53d6\u4e00\u4e2a\u6307\u9488\uff1a

\n
void *GetNamedDSMSegment(const char *name, size_t size,\n                         void (*init_callback) (void *ptr),\n                         bool *found)\n
\n

\u5982\u679c\u7ed9\u5b9a\u540d\u79f0\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u5c1a\u4e0d\u5b58\u5728\uff0c\u8be5\u51fd\u6570\u4f1a\u5206\u914d\u8be5\u6bb5\uff0c\u5e76\u4f7f\u7528\u63d0\u4f9b\u7684 init_callback \u56de\u8c03\u51fd\u6570\u5bf9\u5176\u8fdb\u884c\u521d\u59cb\u5316\u3002\u5982\u679c\u8be5\u6bb5\u5df2\u7ecf\u7531\u53e6\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8fc7\uff0c\u8be5\u51fd\u6570\u5c31\u53ea\u4f1a\u628a\u73b0\u6709\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u9644\u52a0\u5230\u5f53\u524d\u540e\u7aef\u3002

\n

\u4e0e\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559\u7684\u5171\u4eab\u5185\u5b58\u4e0d\u540c\uff0c\u4f7f\u7528 GetNamedDSMSegment \u9884\u7559\u5171\u4eab\u5185\u5b58\u65f6\uff0c\u65e0\u9700\u83b7\u53d6 AddinShmemInitLock\uff0c\u4e5f\u65e0\u9700\u91c7\u53d6\u5176\u4ed6\u63aa\u65bd\u907f\u514d\u7ade\u6001\u6761\u4ef6\u3002\u6b64\u51fd\u6570\u4fdd\u8bc1\u4ec5\u7531\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8be5\u6bb5\uff0c\u5176\u4ed6\u6240\u6709\u540e\u7aef\u83b7\u5f97\u7684\u90fd\u662f\u6307\u5411\u5df2\u5b8c\u5168\u5206\u914d\u5e76\u521d\u59cb\u5316\u7684\u6bb5\u7684\u6307\u9488\u3002

\n

GetNamedDSMSegment \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/test_dsm_registry/test_dsm_registry.c\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n
\n
\n
\n
\n
\n
\n

36.10.12. \u8f7b\u91cf\u7ea7\u9501\uff08LWLocks\uff09

\n
\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.12.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42 LWLocks

\n
\n
\n

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLocks\u3002\u4e0e\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u4e00\u6837\uff0c\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\uff0c\u5e76\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\u3002\u6b64\u94a9\u5b50\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8fd9\u786e\u4fdd\u5b58\u5728\u4e00\u4e2a\u540d\u4e3a tranche_name\u3001\u5305\u542b num_lwlocks \u4e2a LWLocks \u7684\u6570\u7ec4\u3002\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u53d6\u5f97\u8be5\u6570\u7ec4\u7684\u6307\u9488\uff1a

\n
LWLockPadded *GetNamedLWLockTranche(const char *tranche_name)\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.12.2.\u00a0\u542f\u52a8\u540e\u8bf7\u6c42 LWLocks

\n
\n
\n

\n
\n
\n
\n

\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u83b7\u53d6 LWLocks \u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u540e\u8fdb\u884c\uff0c\u4e5f\u65e0\u9700\u501f\u52a9 shmem_request_hook\u3002\u4e3a\u6b64\uff0c\u9996\u5148\u901a\u8fc7\u8c03\u7528\u4e0b\u9762\u7684\u51fd\u6570\u5206\u914d\u4e00\u4e2a tranche_id\uff1a

\n
int LWLockNewTrancheId(void)\n
\n

\u63a5\u4e0b\u6765\uff0c\u521d\u59cb\u5316\u6bcf\u4e2a LWLock\uff0c\u5e76\u628a\u65b0\u7684 tranche_id \u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\uff1a

\n
void LWLockInitialize(LWLock *lock, int tranche_id)\n
\n

\u4e0e\u5171\u4eab\u5185\u5b58\u7c7b\u4f3c\uff0c\u6bcf\u4e2a\u540e\u7aef\u90fd\u5e94\u786e\u4fdd\u53ea\u6709\u4e00\u4e2a\u8fdb\u7a0b\u4f1a\u5206\u914d\u65b0\u7684 tranche_id \u5e76\u521d\u59cb\u5316\u6bcf\u4e00\u4e2a\u65b0\u7684 LWLock\u3002\u4e00\u79cd\u505a\u6cd5\u662f\u4ec5\u5728\u6301\u6709 AddinShmemInitLock \u72ec\u5360\u9501\u7684\u5171\u4eab\u5185\u5b58\u521d\u59cb\u5316\u4ee3\u7801\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u3002\u5982\u679c\u4f7f\u7528 GetNamedDSMSegment\uff0c\u90a3\u4e48\u5728 init_callback \u56de\u8c03\u51fd\u6570\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u5c31\u8db3\u4ee5\u907f\u514d\u7ade\u4e89\u6761\u4ef6\u3002

\n

\u6700\u540e\uff0c\u6bcf\u4e2a\u4f7f\u7528\u8be5 tranche_id \u7684\u540e\u7aef\u90fd\u5e94\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u628a\u5b83\u4e0e\u4e00\u4e2a tranche_name \u5173\u8054\u8d77\u6765\uff1a

\n
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)\n
\n

LWLockNewTrancheId\u3001LWLockInitialize \u548c LWLockRegisterTranche \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_prewarm/autoprewarm.c\u3002

\n
\n
\n
\n
\n
\n
\n

36.10.13. \u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6

\n
\n
\n
\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u5728\u7b49\u5f85\u4e8b\u4ef6\u7c7b\u578b Extension \u4e0b\u5b9a\u4e49\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\uff1a

\n
uint32 WaitEventExtensionNew(const char *wait_event_name)\n
\n

\u8be5\u7b49\u5f85\u4e8b\u4ef6\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u9762\u5411\u7528\u6237\u7684\u81ea\u5b9a\u4e49\u5b57\u7b26\u4e32\u3002\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/worker_spi\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n

\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\u53ef\u4ee5\u5728 pg_stat_activity \u4e2d\u67e5\u770b\uff1a

\n
=# SELECT wait_event_type, wait_event FROM pg_stat_activity\n     WHERE backend_type ~ 'worker_spi';\n wait_event_type |  wait_event\n-----------------+---------------\n Extension       | WorkerSpiMain\n(1 row)\n
\n
\n
\n
\n
\n
\n

36.10.14. \u6ce8\u5165\u70b9

\n
\n
\n
\n

\u7ed9\u5b9a\u540d\u79f0 name \u7684\u6ce8\u5165\u70b9\u53ef\u901a\u8fc7\u4ee5\u4e0b\u5b8f\u58f0\u660e\uff1a

\n
INJECTION_POINT(name, arg);\n
\n

\u670d\u52a1\u5668\u4ee3\u7801\u4e2d\u5df2\u7ecf\u5728\u82e5\u5e72\u5173\u952e\u4f4d\u7f6e\u58f0\u660e\u4e86\u6ce8\u5165\u70b9\u3002\u65b0\u589e\u6ce8\u5165\u70b9\u540e\uff0c\u9700\u8981\u91cd\u65b0\u7f16\u8bd1\u4ee3\u7801\uff0c\u624d\u80fd\u8ba9\u8be5\u6ce8\u5165\u70b9\u51fa\u73b0\u5728\u4e8c\u8fdb\u5236\u6587\u4ef6\u4e2d\u3002\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u4e5f\u53ef\u4ee5\u4f7f\u7528\u540c\u4e00\u4e2a\u5b8f\u5728\u81ea\u5df1\u7684\u4ee3\u7801\u4e2d\u58f0\u660e\u6ce8\u5165\u70b9\u3002\u6ce8\u5165\u70b9\u540d\u79f0\u5e94\u4f7f\u7528\u5c0f\u5199\u5b57\u6bcd\uff0c\u5e76\u7528\u8fde\u5b57\u7b26\u5206\u9694\u5404\u4e2a\u672f\u8bed\u3002arg \u662f\u8fd0\u884c\u65f6\u4f20\u7ed9\u56de\u8c03\u7684\u53ef\u9009\u53c2\u6570\u503c\u3002

\n

\u6267\u884c\u6ce8\u5165\u70b9\u53ef\u80fd\u9700\u8981\u5206\u914d\u5c11\u91cf\u5185\u5b58\uff0c\u800c\u8fd9\u53ef\u80fd\u5931\u8d25\u3002\u5982\u679c\u4f60\u9700\u8981\u5728\u4e00\u4e2a\u4e0d\u5141\u8bb8\u52a8\u6001\u5206\u914d\u7684\u4e34\u754c\u533a\u4e2d\u4f7f\u7528\u6ce8\u5165\u70b9\uff0c\u53ef\u4ee5\u91c7\u7528\u4ee5\u4e0b\u4e24\u6b65\u6cd5\uff1a

\n
INJECTION_POINT_LOAD(name);\nINJECTION_POINT_CACHED(name, arg);\n
\n

\u5728\u8fdb\u5165\u4e34\u754c\u533a\u4e4b\u524d\uff0c\u8c03\u7528 INJECTION_POINT_LOAD\u3002\u5b83\u4f1a\u68c0\u67e5\u5171\u4eab\u5185\u5b58\u72b6\u6001\uff0c\u5e76\u5728\u8be5\u6ce8\u5165\u70b9\u5904\u4e8e\u6fc0\u6d3b\u72b6\u6001\u65f6\u628a\u56de\u8c03\u52a0\u8f7d\u5230\u540e\u7aef\u79c1\u6709\u5185\u5b58\u4e2d\u3002\u5728\u4e34\u754c\u533a\u5185\u90e8\uff0c\u518d\u7528 INJECTION_POINT_CACHED \u6765\u6267\u884c\u56de\u8c03\u3002

\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u4e3a\u4e00\u4e2a\u5df2\u7ecf\u58f0\u660e\u597d\u7684\u6ce8\u5165\u70b9\u9644\u52a0\u56de\u8c03\uff1a

\n
extern void InjectionPointAttach(const char *name,\n                                 const char *library,\n                                 const char *function,\n                                 const void *private_data,\n                                 int private_data_size);\n
\n

name \u662f\u6ce8\u5165\u70b9\u7684\u540d\u79f0\uff1b\u6267\u884c\u5230\u8fbe\u6b64\u6ce8\u5165\u70b9\u65f6\uff0c\u5c06\u6267\u884c\u4ece library \u52a0\u8f7d\u7684\u51fd\u6570\u3002private_data \u662f\u4e00\u5757\u5927\u5c0f\u4e3a private_data_size \u7684\u79c1\u6709\u6570\u636e\u533a\u57df\uff0c\u5728\u6267\u884c\u56de\u8c03\u65f6\u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\u3002

\n

\u4e0b\u9762\u662f\u4e00\u4e2a InjectionPointCallback \u7684\u793a\u4f8b\uff1a

\n
static void\ncustom_injection_callback(const char *name,\n                          const void *private_data,\n                          void *arg)\n{\n    uint32 wait_event_info = WaitEventInjectionPointNew(name);\n\n    pgstat_report_wait_start(wait_event_info);\n    elog(NOTICE, \"%s: executed custom callback\", name);\n    pgstat_report_wait_end();\n}\n
\n

\u8fd9\u4e2a\u56de\u8c03\u4f1a\u4ee5 NOTICE \u7ea7\u522b\u5411\u670d\u52a1\u5668\u9519\u8bef\u65e5\u5fd7\u5199\u5165\u4e00\u6761\u6d88\u606f\uff0c\u4f46\u56de\u8c03\u5b8c\u5168\u53ef\u4ee5\u5b9e\u73b0\u66f4\u590d\u6742\u7684\u903b\u8f91\u3002

\n

\u53e6\u4e00\u79cd\u5b9a\u4e49\u201c\u5230\u8fbe\u6ce8\u5165\u70b9\u65f6\u5e94\u6267\u884c\u4ec0\u4e48\u52a8\u4f5c\u201d\u7684\u65b9\u5f0f\uff0c\u662f\u628a\u6d4b\u8bd5\u4ee3\u7801\u76f4\u63a5\u5199\u5728\u5e38\u89c4\u6e90\u4ee3\u7801\u65c1\u8fb9\u3002\u5982\u679c\u8be5\u52a8\u4f5c\u4f9d\u8d56\u4e8e\u52a0\u8f7d\u6a21\u5757\u65e0\u6cd5\u8bbf\u95ee\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u8fd9\u4f1a\u5f88\u6709\u7528\u3002\u6b64\u65f6\u53ef\u4ee5\u4f7f\u7528 IS_INJECTION_POINT_ATTACHED \u5b8f\u6765\u68c0\u67e5\u67d0\u4e2a\u6ce8\u5165\u70b9\u662f\u5426\u5df2\u9644\u52a0\uff0c\u4f8b\u5982\uff1a

\n
#ifdef USE_INJECTION_POINTS\nif (IS_INJECTION_POINT_ATTACHED(\"before-foobar\"))\n{\n    /* change a local variable if injection point is attached */\n    local_var = 123;\n\n    /* also execute the callback */\n    INJECTION_POINT_CACHED(\"before-foobar\", NULL);\n}\n#endif\n
\n

\u6ce8\u610f\uff0c\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u4e0a\u7684\u56de\u8c03\u4e0d\u4f1a\u7531 IS_INJECTION_POINT_ATTACHED \u5b8f\u6267\u884c\u3002\u5982\u679c\u4f60\u60f3\u6267\u884c\u8be5\u56de\u8c03\uff0c\u5c31\u5fc5\u987b\u50cf\u4e0a\u9762\u7684\u793a\u4f8b\u90a3\u6837\u53e6\u5916\u8c03\u7528 INJECTION_POINT_CACHED\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e5f\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u89e3\u9664\u4e00\u4e2a\u6ce8\u5165\u70b9\uff1a

\n
extern bool InjectionPointDetach(const char *name);\n
\n

\u6210\u529f\u65f6\u8fd4\u56de true\uff0c\u5426\u5219\u8fd4\u56de false\u3002

\n

\u4e00\u4e2a\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u7684\u56de\u8c03\u4f1a\u5728\u6240\u6709\u540e\u7aef\u4e2d\u751f\u6548\uff0c\u5305\u62ec\u5728\u8c03\u7528 InjectionPointAttach \u4e4b\u540e\u624d\u542f\u52a8\u7684\u540e\u7aef\u3002\u5b83\u4f1a\u4e00\u76f4\u4fdd\u6301\u9644\u52a0\u72b6\u6001\uff0c\u76f4\u5230\u670d\u52a1\u5668\u505c\u6b62\uff0c\u6216\u8005\u901a\u8fc7 InjectionPointDetach \u5c06\u5176\u89e3\u9664\u3002

\n

\u76f8\u5173\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 src/test/modules/injection_points\u3002

\n

\u8981\u542f\u7528\u6ce8\u5165\u70b9\uff0c\u4f7f\u7528 configure \u65f6\u9700\u6307\u5b9a --enable-injection-points\uff0c\u4f7f\u7528 Meson \u65f6\u9700\u6307\u5b9a -Dinjection_points=true\u3002

\n
\n
\n
\n
\n
\n

36.10.15. \u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1

\n
\n
\n
\n

\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u53ef\u4ee5\u4f7f\u7528\u5728\u7d2f\u8ba1\u7edf\u8ba1\u7cfb\u7edf\u4e2d\u6ce8\u518c\u7684\u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1\u7c7b\u578b\u3002

\n

\u9996\u5148\uff0c\u5b9a\u4e49\u4e00\u4e2a PgStat_KindInfo\uff0c\u5176\u4e2d\u5305\u542b\u4e0e\u6240\u6ce8\u518c\u81ea\u5b9a\u4e49\u7c7b\u578b\u76f8\u5173\u7684\u5168\u90e8\u4fe1\u606f\u3002\u4f8b\u5982\uff1a

\n
static const PgStat_KindInfo custom_stats = {\n    .name = \"custom_stats\",\n    .fixed_amount = false,\n    .shared_size = sizeof(PgStatShared_Custom),\n    .shared_data_off = offsetof(PgStatShared_Custom, stats),\n    .shared_data_len = sizeof(((PgStatShared_Custom *) 0)->stats),\n    .pending_size = sizeof(PgStat_StatCustomEntry),\n}\n
\n

\u7136\u540e\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8fd9\u79cd\u81ea\u5b9a\u4e49\u7c7b\u578b\u7684\u540e\u7aef\uff0c\u90fd\u9700\u8981\u4f7f\u7528 pgstat_register_kind \u6ce8\u518c\u5b83\uff0c\u5e76\u6307\u5b9a\u4e00\u4e2a\u7528\u4e8e\u5b58\u50a8\u8be5\u7c7b\u7edf\u8ba1\u6761\u76ee\u7684\u552f\u4e00 ID\uff1a

\n
extern PgStat_Kind pgstat_register_kind(PgStat_Kind kind,\n                                        const PgStat_KindInfo *kind_info);\n
\n

\u5728\u5f00\u53d1\u65b0\u6269\u5c55\u65f6\uff0c\u5e94\u5c06 PGSTAT_KIND_EXPERIMENTAL \u7528\u4f5c kind\u3002\u5f53\u4f60\u51c6\u5907\u628a\u6269\u5c55\u53d1\u5e03\u7ed9\u7528\u6237\u65f6\uff0c\u8bf7\u5728 Custom Cumulative Statistics \u9875\u9762\u4e0a\u9884\u7559\u4e00\u4e2a kind ID\u3002

\n

\u5173\u4e8e PgStat_KindInfo API \u7684\u7ec6\u8282\uff0c\u53ef\u89c1 src/include/utils/pgstat_internal.h\u3002

\n

\u5df2\u6ce8\u518c\u7684\u7edf\u8ba1\u7c7b\u578b\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u540d\u79f0\u4ee5\u53ca\u4e00\u4e2a\u5728\u5171\u4eab\u5185\u5b58\u4e2d\u4f9b\u6574\u4e2a\u670d\u52a1\u5668\u5171\u4eab\u7684\u552f\u4e00 ID\u3002\u6bcf\u4e2a\u4f7f\u7528\u81ea\u5b9a\u4e49\u7edf\u8ba1\u7c7b\u578b\u7684\u540e\u7aef\u90fd\u4f1a\u7ef4\u62a4\u4e00\u4e2a\u672c\u5730\u7f13\u5b58\uff0c\u7528\u6765\u4fdd\u5b58\u5404\u4e2a\u81ea\u5b9a\u4e49 PgStat_KindInfo \u7684\u4fe1\u606f\u3002

\n

\u5e94\u5c06\u5b9e\u73b0\u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1\u7c7b\u578b\u7684\u6269\u5c55\u6a21\u5757\u52a0\u5165shared_preload_libraries\uff0c\u4ee5\u4fbf\u5728 PostgreSQL \u542f\u52a8\u671f\u95f4\u5c3d\u65e9\u8f7d\u5165\u3002

\n

\u5c55\u793a\u5982\u4f55\u6ce8\u518c\u5e76\u4f7f\u7528\u81ea\u5b9a\u4e49\u7edf\u8ba1\u4fe1\u606f\u7684\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/injection_points\u3002

\n
\n
\n
\n
\n
\n

36.10.16. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
", "manual_path": "/docs/18/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/18/protocol-overview.html", "method": "same-major semantic node", "sha256": "3f1aa8bd4dbef58e9a82e8cf4c82829a4df7416cfa83dd61c18e9e25060f22da", "language": "zh", "matched_nodes": ["#PROTOCOL-OVERVIEW/div[9]/p[1]/span[2]/span[0]"]}, {"url": "/docs/18/xfunc-c.html", "method": "same-major semantic node", "sha256": "4b35ab16ac85cc22b5c37555941784a2fd0a1b66b507e9dfff9a239102c15e77", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/div[2]/div[0]", "#XFUNC-C/div[10]/div[2]/p[2]", "#XFUNC-C/div[10]/div[3]/div[0]", "#XFUNC-C/div[10]/div[3]/div[2]/p[1]", "#XFUNC-C/div[10]/div[3]/div[3]/p[1]", "#XFUNC-C/div[10]/div[3]/div[3]/p[2]", "#XFUNC-C/div[10]/div[4]/div[0]", "#XFUNC-C/div[10]/div[4]/div[2]/p[1]", "#XFUNC-C/div[10]/div[4]/div[3]/p[1]", "#XFUNC-C/div[10]/div[4]/div[3]/p[2]", "#XFUNC-C/div[10]/div[4]/div[3]/p[3]", "#XFUNC-C/div[10]/div[4]/div[3]/p[4]", "#XFUNC-C/div[10]/div[4]/div[3]/p[5]", "#XFUNC-C/div[10]/p[1]", "#XFUNC-C/div[11]/p[10]", "#XFUNC-C/div[11]/p[1]", "#XFUNC-C/div[11]/p[2]", "#XFUNC-C/div[11]/p[6]", "#XFUNC-C/div[11]/p[7]", "#XFUNC-C/div[11]/p[8]", "#XFUNC-C/div[12]/div[7]/p[1]", "#XFUNC-C/div[12]/div[8]/p[1]", "#XFUNC-C/div[12]/p[11]", "#XFUNC-C/div[12]/p[13]", "#XFUNC-C/div[12]/p[14]", "#XFUNC-C/div[12]/p[16]", "#XFUNC-C/div[12]/p[18]", "#XFUNC-C/div[12]/p[19]", "#XFUNC-C/div[12]/p[1]", "#XFUNC-C/div[12]/p[21]", "#XFUNC-C/div[12]/p[22]", "#XFUNC-C/div[12]/p[24]", "#XFUNC-C/div[12]/p[25]", "#XFUNC-C/div[12]/p[27]", "#XFUNC-C/div[12]/p[28]", "#XFUNC-C/div[12]/p[3]", "#XFUNC-C/div[12]/p[4]", "#XFUNC-C/div[12]/p[6]", "#XFUNC-C/div[12]/p[9]", "#XFUNC-C/div[13]/div[19]/p[1]", "#XFUNC-C/div[13]/p[10]", "#XFUNC-C/div[13]/p[12]", "#XFUNC-C/div[13]/p[13]", "#XFUNC-C/div[13]/p[15]", "#XFUNC-C/div[13]/p[20]", "#XFUNC-C/div[13]/p[22]", "#XFUNC-C/div[13]/p[24]", "#XFUNC-C/div[13]/p[26]", "#XFUNC-C/div[13]/p[28]", "#XFUNC-C/div[13]/p[2]", "#XFUNC-C/div[13]/p[3]", "#XFUNC-C/div[13]/p[4]", "#XFUNC-C/div[13]/p[6]", "#XFUNC-C/div[13]/p[8]", "#XFUNC-C/div[14]/p[1]", "#XFUNC-C/div[14]/p[2]", "#XFUNC-C/div[14]/p[4]", "#XFUNC-C/div[14]/p[6]", "#XFUNC-C/div[15]/div[1]/div[0]", "#XFUNC-C/div[15]/div[1]/p[3]", "#XFUNC-C/div[15]/div[1]/p[5]", "#XFUNC-C/div[15]/div[1]/p[6]", "#XFUNC-C/div[15]/div[1]/p[8]", "#XFUNC-C/div[15]/div[1]/p[9]", "#XFUNC-C/div[15]/div[2]/div[0]", "#XFUNC-C/div[15]/div[2]/p[1]", "#XFUNC-C/div[15]/div[2]/p[3]", "#XFUNC-C/div[15]/div[2]/p[5]", "#XFUNC-C/div[16]/div[1]/div[0]", "#XFUNC-C/div[16]/div[2]/div[0]", "#XFUNC-C/div[16]/div[2]/p[1]", "#XFUNC-C/div[16]/div[2]/p[3]", "#XFUNC-C/div[16]/div[2]/p[5]", "#XFUNC-C/div[16]/div[2]/p[6]", "#XFUNC-C/div[16]/div[2]/p[8]", "#XFUNC-C/div[17]/p[1]", "#XFUNC-C/div[17]/p[3]", "#XFUNC-C/div[17]/p[4]", "#XFUNC-C/div[18]/p[10]", "#XFUNC-C/div[18]/p[12]", "#XFUNC-C/div[18]/p[13]", "#XFUNC-C/div[18]/p[15]", "#XFUNC-C/div[18]/p[16]", "#XFUNC-C/div[18]/p[18]", "#XFUNC-C/div[18]/p[19]", "#XFUNC-C/div[18]/p[1]", "#XFUNC-C/div[18]/p[20]", "#XFUNC-C/div[18]/p[3]", "#XFUNC-C/div[18]/p[4]", "#XFUNC-C/div[18]/p[6]", "#XFUNC-C/div[18]/p[7]", "#XFUNC-C/div[19]/p[10]", "#XFUNC-C/div[19]/p[1]", "#XFUNC-C/div[19]/p[2]", "#XFUNC-C/div[19]/p[4]", "#XFUNC-C/div[19]/p[6]", "#XFUNC-C/div[19]/p[7]", "#XFUNC-C/div[19]/p[8]", "#XFUNC-C/div[19]/p[9]", "#XFUNC-C/div[1]/dl[0]/dt[0]", "#XFUNC-C/div[1]/dl[0]/dt[10]", "#XFUNC-C/div[1]/dl[0]/dt[12]", "#XFUNC-C/div[1]/dl[0]/dt[13]", "#XFUNC-C/div[1]/dl[0]/dt[14]", "#XFUNC-C/div[1]/dl[0]/dt[15]", "#XFUNC-C/div[1]/dl[0]/dt[1]", "#XFUNC-C/div[1]/dl[0]/dt[2]", "#XFUNC-C/div[1]/dl[0]/dt[3]", "#XFUNC-C/div[1]/dl[0]/dt[4]", "#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[20]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[20]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[20]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[20]/p[2]", "#XFUNC-C/div[20]/p[4]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[12]", "#XFUNC-C/div[5]/p[14]", "#XFUNC-C/div[5]/p[16]", "#XFUNC-C/div[5]/p[18]", "#XFUNC-C/div[5]/p[19]", "#XFUNC-C/div[5]/p[22]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[0]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[3]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[10]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[17]", "#XFUNC-C/div[7]/p[18]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[20]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[7]", "#XFUNC-C/div[7]/p[8]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[4]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[5]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[6]", "#XFUNC-C/div[8]/p[1]", "#XFUNC-C/div[8]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[11]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[1]/p[2]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[3]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[5]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[7]/p[0]", "#XFUNC-C/div[9]/div[5]/dl[0]/dd[9]/p[0]", "#XFUNC-C/div[9]/div[6]/h3[0]", "#XFUNC-C/div[9]/div[6]/p[1]", "#XFUNC-C/div[9]/p[1]", "#XFUNC-C/div[9]/p[2]", "#XFUNC-C/div[9]/p[4]", "#XFUNC-C/div[9]/p[7]", "#XFUNC-C/div[9]/p[8]", "#XFUNC-C/p[3]"]}], "language": "zh", "original_text": {"/versions/18/description/0": "dynamically-loaded C functions", "/versions/18/facts/0/label": "Kind", "/versions/18/facts/0/value": "Native function language", "/versions/18/facts/1/label": "Trusted", "/versions/18/facts/2/label": "Validator"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "126e9ec2b5157e7be6f2d1aaace3449ca213b73b9f2a7d82748ff9e6afc13a05"}, "comparison_data": {"kind": "Native function language", "handler": "", "trusted": "f", "validator": "fmgr_c_validator"}, "comparison_hash": "e8a219c1a26602affef41a21da26d099cf721ba42739cb7b056898c9e2d6fbe6", "manual_language": "zh"}, "19": {"facts": [{"label": "\u79cd\u7c7b", "value": "\u539f\u751f\u51fd\u6570\u8bed\u8a00"}, {"label": "\u53ef\u4fe1", "value": "f"}, {"label": "\u6821\u9a8c\u51fd\u6570", "value": "fmgr_c_validator"}], "tables": [], "aliases": [], "catalog": {"oid": "13", "descr": "dynamically-loaded C functions", "lanacl": "_null_", "lanispl": "f", "lanname": "c", "lanowner": "POSTGRES", "laninline": "0", "oid_symbol": "ClanguageId", "lanpltrusted": "f", "lanvalidator": "fmgr_c_validator", "lanplcallfoid": "0"}, "related": [], "release": {"ref": "https://ftp.postgresql.org/pub/source/v19beta4/postgresql-19beta4.tar.bz2", "label": "19beta4", "major": "19", "channel": "preview", "revision": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86", "source_sha256": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86", "catalog_fingerprint": "62fbf1a3689dbe8bf7e6b3372cfe6fbf867581427b3858a94c8419b77a4d2d1d"}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v19beta4/postgresql-19beta4.tar.bz2", "label": "Matching PostgreSQL source archive", "sha256": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}, {"url": "https://pg.center/docs/19/xfunc-c.html", "path": "xfunc-c.html", "label": "PostgreSQL 19 English manual", "sha256": "d10924ba0f29357c84d2427c3329e05828e7ebd646444296568b8ee8f230b347", "language": "en", "original_url": "/docs/19/xfunc-c.html"}], "sections": [], "signature": "", "attributes": {"kind": "Native function language", "handler": "", "trusted": "f", "validator": "fmgr_c_validator"}, "description": ["\u52a8\u6001\u52a0\u8f7d\u7684 C \u51fd\u6570"], "manual_html": "
\n
\n
\n
\n

\n
\n
\n

36.10.\u00a0C \u8bed\u8a00\u51fd\u6570

\n
\n
\n

\n
\n
\n
\n

\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

\n

\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

\n
\n
\n
\n
\n

36.10.1. \u52a8\u6001\u8f7d\u5165

\n
\n
\n
\n

\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u904d\u5386\u901a\u5f80\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u6216\u8005

\n
PG_MODULE_MAGIC_EXT(parameters);\n
\n

PG_MODULE_MAGIC_EXT \u8fd9\u79cd\u5f62\u5f0f\u5141\u8bb8\u4e3a\u6a21\u5757\u6307\u5b9a\u9644\u52a0\u4fe1\u606f\uff1b\u76ee\u524d\u53ef\u4ee5\u6dfb\u52a0\u540d\u79f0\u548c/\u6216\u7248\u672c\u5b57\u7b26\u4e32\u3002\uff08\u5c06\u6765\u53ef\u80fd\u5141\u8bb8\u66f4\u591a\u5b57\u6bb5\u3002\uff09\u53ef\u4ee5\u5199\u6210\u8fd9\u6837\uff1a

\n
PG_MODULE_MAGIC_EXT(\n    .name = \"my_module_name\",\n    .version = \"1.2.3\"\n);\n
\n

\u4e4b\u540e\uff0c\u540d\u79f0\u548c\u7248\u672c\u53ef\u4ee5\u901a\u8fc7 pg_get_loaded_modules() \u51fd\u6570\u67e5\u770b\u3002\u7248\u672c\u5b57\u7b26\u4e32\u7684\u5177\u4f53\u542b\u4e49\u4e0d\u53d7 PostgreSQL \u9650\u5236\uff0c\u4f46\u5efa\u8bae\u91c7\u7528\u8bed\u4e49\u5316\u7248\u672c\u89c4\u5219\u3002

\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u5305\u542b\u4e00\u4e2a\u521d\u59cb\u5316\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init\u7684\u51fd\u6570\uff0c\u90a3\u4e2a\u51fd\u6570\u5c06\u5728\u52a0\u8f7d\u6587\u4ef6\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u4efb\u4f55\u53c2\u6570\uff0c\u5e94\u8be5\u8fd4\u56devoid\u3002\u76ee\u524d\u6ca1\u6709\u529e\u6cd5\u5378\u8f7d\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u3002

\n
\n
\n
\n
\n
\n

36.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u5c06\u5b83\u4eec\u4f20\u5165\u51fd\u6570\u548c\u4ece\u51fd\u6570\u4f20\u51fa\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012\u30014 \u6216 8 \u5b57\u8282\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a036.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a036.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u51fd\u6570\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a036.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a036.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
\u6587\u672ctext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u8981\u8c03\u7528\u53e6\u4e00\u4e2a\u7248\u672c-1 \u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528 DirectFunctionCalln(func, arg1, ..., argn)\u3002\u8fd9\u5728\u4f60\u60f3\u8c03\u7528\u6807\u51c6\u5185\u90e8\u5e93\u4e2d\u5b9a\u4e49\u7684\u51fd\u6570\u65f6\u5c24\u5176\u6709\u7528\uff0c\u56e0\u4e3a\u5b83\u63d0\u4f9b\u4e86\u4e0e\u5176 SQL \u7b7e\u540d\u76f8\u4f3c\u7684\u63a5\u53e3\u3002

\n

\u8fd9\u4e9b\u4fbf\u5229\u51fd\u6570\u4ee5\u53ca\u7c7b\u4f3c\u51fd\u6570\u90fd\u53ef\u4ee5\u5728 fmgr.h \u4e2d\u627e\u5230\u3002DirectFunctionCalln \u7cfb\u5217\u628a C \u51fd\u6570\u540d\u4f5c\u4e3a\u5176\u7b2c\u4e00\u4e2a\u53c2\u6570\u3002\u53e6\u6709 OidFunctionCalln \u7b49\u4e00\u4e9b\u53d8\u4f53\uff0c\u5b83\u4eec\u63a5\u6536\u76ee\u6807\u51fd\u6570\u7684 OID\u3002\u6240\u6709\u8fd9\u4e9b\u51fd\u6570\u90fd\u8981\u6c42\u4ee5 Datum \u5f62\u5f0f\u63d0\u4f9b\u51fd\u6570\u53c2\u6570\uff0c\u8fd4\u56de\u503c\u4e5f\u540c\u6837\u662f Datum\u3002\u6ce8\u610f\uff0c\u4f7f\u7528\u8fd9\u4e9b\u4fbf\u5229\u51fd\u6570\u65f6\uff0c\u53c2\u6570\u548c\u7ed3\u679c\u90fd\u4e0d\u80fd\u4e3a NULL\u3002

\n

\u4f8b\u5982\uff0c\u8981\u5728 C \u4e2d\u8c03\u7528 starts_with(text, text)\uff0c\u4f60\u53ef\u4ee5\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\u67e5\u5230\u5b83\u7684 C \u5b9e\u73b0\u662f Datum text_starts_with(PG_FUNCTION_ARGS) \u51fd\u6570\u3002\u901a\u5e38\u4f60\u4f1a\u7528 DirectFunctionCall2(text_starts_with, ...) \u6765\u8c03\u7528\u5b83\u3002\u4e0d\u8fc7\uff0cstarts_with(text, text) \u9700\u8981\u6392\u5e8f\u89c4\u5219\u4fe1\u606f\uff0c\u56e0\u6b64\u5982\u679c\u8fd9\u6837\u8c03\u7528\uff0c\u4f1a\u56e0\u201c\u65e0\u6cd5\u786e\u5b9a\u5b57\u7b26\u4e32\u6bd4\u8f83\u8be5\u4f7f\u7528\u54ea\u4e00\u79cd\u6392\u5e8f\u89c4\u5219\u201d\u800c\u5931\u8d25\u3002\u4f60\u5fc5\u987b\u6539\u7528 DirectFunctionCall2Coll(text_starts_with, ...)\uff0c\u5e76\u63d0\u4f9b\u6240\u9700\u7684\u6392\u5e8f\u89c4\u5219\uff0c\u901a\u5e38\u5c31\u662f\u4ece PG_GET_COLLATION() \u4f20\u9012\u8fdb\u6765\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u6240\u793a\u3002

\n

fmgr.h \u8fd8\u63d0\u4f9b\u4e86\u4fbf\u4e8e\u5728 C \u7c7b\u578b\u548c Datum \u4e4b\u95f4\u8f6c\u6362\u7684\u5b8f\u3002\u4f8b\u5982\uff0c\u8981\u628a Datum \u8f6c\u6210 text*\uff0c\u53ef\u4ee5\u4f7f\u7528 DatumGetTextPP(X)\u3002\u867d\u7136\u67d0\u4e9b\u7c7b\u578b\u4e3a\u53cd\u5411\u8f6c\u6362\u63d0\u4f9b\u4e86\u540d\u4e3a TypeGetDatum(X) \u4e4b\u7c7b\u7684\u5b8f\uff0c\u4f46 text* \u6ca1\u6709\uff1b\u5bf9\u5b83\u800c\u8a00\uff0c\u76f4\u63a5\u4f7f\u7528\u901a\u7528\u5b8f PointerGetDatum(X) \u5373\u53ef\u3002\u5982\u679c\u4f60\u7684\u6269\u5c55\u5b9a\u4e49\u4e86\u989d\u5916\u7684\u7c7b\u578b\uff0c\u901a\u5e38\u4e5f\u5f88\u65b9\u4fbf\u4e3a\u8fd9\u4e9b\u7c7b\u578b\u5b9a\u4e49\u7c7b\u4f3c\u7684\u5b8f\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n#include \"varatt.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = palloc_object(Point);\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy(VARDATA(new_t),          /* destination */\n           VARDATA_ANY(t),          /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n/* A wrapper around starts_with(text, text) */\n\nPG_FUNCTION_INFO_V1(t_starts_with);\n\nDatum\nt_starts_with(PG_FUNCTION_ARGS)\n{\n    text       *t1 = PG_GETARG_TEXT_PP(0);\n    text       *t2 = PG_GETARG_TEXT_PP(1);\n    Oid         collid = PG_GET_COLLATION();\n    bool        result;\n\n    result = DatumGetBool(DirectFunctionCall2Coll(text_starts_with,\n                                                  collid,\n                                                  PointerGetDatum(t1),\n                                                  PointerGetDatum(t2)));\n    PG_RETURN_BOOL(result);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION t_starts_with(text, text) RETURNS boolean\n     AS 'DIRECTORY/funcs', 't_starts_with'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a036.10.9\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a037\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a057\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

\n
\n
\n
\n
\n
\n

36.10.4. \u7f16\u5199\u4ee3\u7801

\n
\n
\n
\n

\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a036.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

36.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 13.0 \u8d77\u9002\u7528\uff1b\u66f4\u65e9\u7248\u672c\u4f7f\u7528\u7684\u662f gcc \u7f16\u8bd1\u5668\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f GCC \u7684 -fPIC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u7f16\u8bd1\u5668\u9009\u9879\u662f GCC \u7684 -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

36.10.6. \u670d\u52a1\u5668 API \u548c ABI \u7a33\u5b9a\u6027\u6307\u5357

\n
\n
\n
\n

\u672c\u8282\u5411\u6269\u5c55\u548c\u5176\u4ed6\u670d\u52a1\u5668\u63d2\u4ef6\u7684\u4f5c\u8005\u63d0\u4f9b\u6709\u5173 PostgreSQL \u670d\u52a1\u5668 API \u4e0e ABI \u7a33\u5b9a\u6027\u7684\u6307\u5bfc\u3002

\n
\n
\n
\n
\n

\n
\n
\n

36.10.6.1.\u00a0\u6982\u8ff0

\n
\n
\n

\n
\n
\n
\n

PostgreSQL \u670d\u52a1\u5668\u4e3a\u63d2\u4ef6\u63d0\u4f9b\u4e86\u591a\u4e2a\u8fb9\u754c\u6e05\u6670\u7684 API\uff0c\u4f8b\u5982\u672c\u7ae0\u4ecb\u7ecd\u7684\u51fd\u6570\u7ba1\u7406\u5668 fmgr\u3001SPI\uff08\u7b2c 45 \u7ae0\uff09\u4ee5\u53ca\u4e13\u4e3a\u6269\u5c55\u8bbe\u8ba1\u7684\u5404\u79cd\u94a9\u5b50\u3002\u8fd9\u4e9b\u63a5\u53e3\u7ecf\u8fc7\u8c28\u614e\u7ef4\u62a4\uff0c\u4ee5\u4fdd\u6301\u957f\u671f\u7a33\u5b9a\u6027\u548c\u517c\u5bb9\u6027\u3002\u4e0d\u8fc7\uff0c\u670d\u52a1\u5668\u4e2d\u5168\u90e8\u5168\u5c40\u51fd\u6570\u548c\u53d8\u91cf\u5b9e\u9645\u4e0a\u90fd\u6784\u6210\u4e86\u53ef\u516c\u5f00\u4f7f\u7528\u7684 API\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u5728\u8bbe\u8ba1\u65f6\u5e76\u672a\u8003\u8651\u53ef\u6269\u5c55\u6027\u548c\u957f\u671f\u7a33\u5b9a\u6027\u3002

\n

\u56e0\u6b64\uff0c\u867d\u7136\u4f7f\u7528\u8fd9\u4e9b\u63a5\u53e3\u662f\u5b8c\u5168\u5141\u8bb8\u7684\uff0c\u4f46\u8d8a\u662f\u504f\u79bb\u90a3\u4e9b\u4e45\u7ecf\u5b9e\u8df5\u8003\u9a8c\u7684\u8def\u5f84\uff0c\u5c06\u6765\u9047\u5230 API \u6216 ABI \u517c\u5bb9\u6027\u95ee\u9898\u7684\u53ef\u80fd\u6027\u5c31\u8d8a\u5927\u3002\u9f13\u52b1\u6269\u5c55\u4f5c\u8005\u53cd\u9988\u81ea\u5df1\u7684\u9700\u6c42\uff0c\u4ee5\u4fbf\u968f\u7740\u65f6\u95f4\u63a8\u79fb\u548c\u65b0\u7528\u6cd5\u7684\u51fa\u73b0\uff0c\u67d0\u4e9b\u63a5\u53e3\u80fd\u591f\u88ab\u89c6\u4e3a\u66f4\u7a33\u5b9a\uff0c\u6216\u8005\u53ef\u4ee5\u52a0\u5165\u65b0\u7684\u3001\u8bbe\u8ba1\u66f4\u5b8c\u5584\u7684\u63a5\u53e3\u3002

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36.10.6.2.\u00a0API \u517c\u5bb9\u6027

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\n

API\uff0c\u5373\u5e94\u7528\u7a0b\u5e8f\u7f16\u7a0b\u63a5\u53e3\uff0c\u662f\u7f16\u8bd1\u65f6\u4f7f\u7528\u7684\u63a5\u53e3\u3002

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36.10.6.2.1.\u00a0Major Versions
\n
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\u5728 PostgreSQL \u4e0d\u540c\u4e3b\u7248\u672c\u4e4b\u95f4\uff0c\u4e0d\u627f\u8bfa API \u517c\u5bb9\u6027\u3002\u56e0\u6b64\uff0c\u6269\u5c55\u4ee3\u7801\u53ef\u80fd\u9700\u8981\u4fee\u6539\u6e90\u4ee3\u7801\u624d\u80fd\u540c\u65f6\u652f\u6301\u591a\u4e2a\u4e3b\u7248\u672c\u3002\u8fd9\u7c7b\u5dee\u5f02\u901a\u5e38\u53ef\u4ee5\u901a\u8fc7\u9884\u5904\u7406\u5668\u6761\u4ef6\uff08\u4f8b\u5982 #if PG_VERSION_NUM >= 160000\uff09\u6765\u7ba1\u7406\u3002\u90a3\u4e9b\u4f7f\u7528\u4e86\u8fb9\u754c\u6e05\u6670\u63a5\u53e3\u4e4b\u5916\u80fd\u529b\u7684\u590d\u6742\u6269\u5c55\uff0c\u901a\u5e38\u6bcf\u4e2a\u670d\u52a1\u5668\u4e3b\u7248\u672c\u90fd\u9700\u8981\u505a\u5c11\u91cf\u8fd9\u7c7b\u4fee\u6539\u3002

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36.10.6.2.2.\u00a0Minor Versions
\n
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PostgreSQL \u4f1a\u5c3d\u529b\u907f\u514d\u5728\u5c0f\u7248\u672c\u53d1\u5e03\u4e2d\u7834\u574f\u670d\u52a1\u5668 API\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u80fd\u9488\u5bf9\u67d0\u4e2a\u5c0f\u7248\u672c\u7f16\u8bd1\u5e76\u6b63\u5e38\u5de5\u4f5c\u7684\u6269\u5c55\u4ee3\u7801\uff0c\u4e5f\u5e94\u5f53\u80fd\u591f\u9488\u5bf9\u540c\u4e00\u4e3b\u7248\u672c\u7684\u5176\u4ed6\u4efb\u610f\u5c0f\u7248\u672c\uff08\u65e0\u8bba\u8fc7\u53bb\u8fd8\u662f\u5c06\u6765\uff09\u7f16\u8bd1\u5e76\u6b63\u5e38\u5de5\u4f5c\u3002

\n

\u5982\u679c\u786e\u5b9e\u9700\u8981\u505a\u51fa\u53d8\u66f4\uff0c\u4e5f\u4f1a\u5728\u8003\u8651\u6269\u5c55\u9700\u6c42\u7684\u524d\u63d0\u4e0b\u8c28\u614e\u7ba1\u7406\u3002\u8fd9\u7c7b\u53d8\u66f4\u4f1a\u5728\u53d1\u5e03\u8bf4\u660e\uff08\u9644\u5f55\u00a0E\uff09\u4e2d\u8fdb\u884c\u8bf4\u660e\u3002

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36.10.6.3.\u00a0ABI \u517c\u5bb9\u6027

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ABI\uff0c\u5373\u5e94\u7528\u7a0b\u5e8f\u4e8c\u8fdb\u5236\u63a5\u53e3\uff0c\u662f\u8fd0\u884c\u65f6\u4f7f\u7528\u7684\u63a5\u53e3\u3002

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36.10.6.3.1.\u00a0Major Versions
\n
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\u4e0d\u540c\u4e3b\u7248\u672c\u7684\u670d\u52a1\u5668\u5728 ABI \u4e0a\u662f\u6709\u610f\u4e0d\u517c\u5bb9\u7684\u3002\u56e0\u6b64\uff0c\u4f7f\u7528\u670d\u52a1\u5668 API \u7684\u6269\u5c55\u5fc5\u987b\u9488\u5bf9\u6bcf\u4e00\u4e2a\u4e3b\u7248\u672c\u91cd\u65b0\u7f16\u8bd1\u3002\u5305\u542b PG_MODULE_MAGIC\uff08\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\uff09\u53ef\u4ee5\u786e\u4fdd\u9488\u5bf9\u67d0\u4e2a\u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u4ee3\u7801\u4f1a\u88ab\u5176\u4ed6\u4e3b\u7248\u672c\u62d2\u7edd\u3002

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36.10.6.3.2.\u00a0Minor Versions
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PostgreSQL \u4f1a\u5c3d\u529b\u907f\u514d\u5728\u5c0f\u7248\u672c\u53d1\u5e03\u4e2d\u7834\u574f\u670d\u52a1\u5668 ABI\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u9488\u5bf9\u4efb\u610f\u4e00\u4e2a\u5c0f\u7248\u672c\u7f16\u8bd1\u7684\u6269\u5c55\uff0c\u5e94\u5f53\u80fd\u4e0e\u540c\u4e00\u4e3b\u7248\u672c\u8fc7\u53bb\u6216\u5c06\u6765\u7684\u5176\u4ed6\u4efb\u610f\u5c0f\u7248\u672c\u4e00\u8d77\u5de5\u4f5c\u3002

\n

\u5982\u679c\u786e\u5b9e\u9700\u8981\u53d8\u66f4\uff0cPostgreSQL \u4f1a\u5c3d\u91cf\u9009\u62e9\u4fb5\u5165\u6027\u6700\u5c0f\u7684\u65b9\u5f0f\uff0c\u4f8b\u5982\u628a\u65b0\u5b57\u6bb5\u585e\u8fdb\u586b\u5145\u7a7a\u95f4\uff0c\u6216\u8005\u9644\u52a0\u5230\u7ed3\u6784\u4f53\u672b\u5c3e\u3002\u8fd9\u7c7b\u4fee\u6539\u901a\u5e38\u4e0d\u5e94\u5f71\u54cd\u6269\u5c55\uff0c\u9664\u975e\u6269\u5c55\u4f7f\u7528\u4e86\u975e\u5e38\u4e0d\u5bfb\u5e38\u7684\u4ee3\u7801\u6a21\u5f0f\u3002

\n

\u7136\u800c\uff0c\u5728\u6781\u5c11\u6570\u60c5\u51b5\u4e0b\uff0c\u5373\u4f7f\u662f\u8fd9\u79cd\u975e\u4fb5\u5165\u5f0f\u53d8\u66f4\u4e5f\u53ef\u80fd\u4e0d\u73b0\u5b9e\u751a\u81f3\u4e0d\u53ef\u80fd\u505a\u5230\u3002\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\u65f6\uff0c\u4e5f\u4f1a\u5728\u8003\u8651\u6269\u5c55\u9700\u6c42\u7684\u524d\u63d0\u4e0b\u8c28\u614e\u7ba1\u7406\u8be5\u53d8\u66f4\u3002\u8fd9\u7c7b\u53d8\u66f4\u540c\u6837\u4f1a\u8bb0\u5f55\u5728\u53d1\u5e03\u8bf4\u660e\uff08\u9644\u5f55\u00a0E\uff09\u4e2d\u3002

\n

\u4f46\u8bf7\u6ce8\u610f\uff0c\u670d\u52a1\u5668\u4e2d\u6709\u5f88\u591a\u90e8\u5206\u5e76\u4e0d\u662f\u4f5c\u4e3a\u53ef\u516c\u5f00\u4f7f\u7528\u7684 API \u6765\u8bbe\u8ba1\u548c\u7ef4\u62a4\u7684\uff08\u800c\u4e14\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u5176\u771f\u5b9e\u8fb9\u754c\u4e5f\u5e76\u4e0d\u6e05\u6670\uff09\u3002\u5982\u679c\u51fa\u73b0\u7d27\u6025\u9700\u6c42\uff0c\u5bf9\u8fd9\u4e9b\u90e8\u5206\u8fdb\u884c\u4fee\u6539\u65f6\uff0c\u81ea\u7136\u4f1a\u6bd4\u4fee\u6539\u90a3\u4e9b\u8fb9\u754c\u6e05\u695a\u4e14\u5e7f\u6cdb\u4f7f\u7528\u7684\u63a5\u53e3\u65f6\u66f4\u5c11\u8003\u8651\u6269\u5c55\u4ee3\u7801\u7684\u517c\u5bb9\u6027\u3002

\n

\u6b64\u5916\uff0c\u5728\u7f3a\u4e4f\u81ea\u52a8\u5316\u68c0\u6d4b\u8fd9\u7c7b\u53d8\u5316\u7684\u673a\u5236\u65f6\uff0c\u8fd9\u5e76\u4e0d\u80fd\u6784\u6210\u4e25\u683c\u4fdd\u8bc1\uff1b\u4e0d\u8fc7\u4ece\u5386\u53f2\u4e0a\u770b\uff0c\u8fd9\u79cd\u7834\u574f\u6027\u53d8\u5316\u6781\u4e3a\u7f55\u89c1\u3002

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36.10.7. \u590d\u5408\u7c7b\u578b\u53c2\u6570

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\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u51fd\u6570\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

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36.10.8. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
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\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.9. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_INT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

36.10.10. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a036.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
\n
\n
\n
\n
\n

36.10.11. \u5171\u4eab\u5185\u5b58

\n
\n
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36.10.11.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

\n
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\n
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\n

\u63d2\u4ef6\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u3002\u8981\u505a\u5230\u8fd9\u4e00\u70b9\uff0c\u63d2\u4ef6\u7684\u5171\u4eab\u5e93\u5fc5\u987b\u901a\u8fc7shared_preload_libraries\u9884\u52a0\u8f7d\u3002\u8be5\u5171\u4eab\u5e93\u8fd8\u5e94\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c\u56de\u8c03\uff0c\u4ee5\u4fbf\u5728\u7cfb\u7edf\u542f\u52a8\u7684\u5408\u9002\u9636\u6bb5\u521d\u59cb\u5316\u5171\u4eab\u5185\u5b58\u3002\u793a\u4f8b\u5982\u4e0b\uff1a

\n
typedef struct MyShmemData {\n    LWLock      lock;    /* protects the fields below */\n\n    ... shared memory contents ...\n} MyShmemData;\n\nstatic MyShmemData *MyShmem;    /* pointer to the struct in shared memory */\n\nstatic void my_shmem_request(void *arg);\nstatic void my_shmem_init(void *arg);\n\nconst ShmemCallbacks my_shmem_callbacks = {\n    .request_fn = my_shmem_request,\n    .init_fn = my_shmem_init,\n};\n\n/*\n * Module load callback\n */\nvoid\n_PG_init(void)\n{\n    /*\n     * In order to create our shared memory area, we have to be loaded via\n     * shared_preload_libraries.\n     */\n    if (!process_shared_preload_libraries_in_progress)\n        return;\n\n    /* Register our shared memory needs */\n    RegisterShmemCallbacks(&my_shmem_callbacks);\n}\n\n/* callback to request shmem space */\nstatic void\nmy_shmem_request(void *arg)\n{\n    ShmemRequestStruct(.name = \"My shmem area\",\n                       .size = sizeof(MyShmemData),\n                       .ptr = (void **) &MyShmem,\n        );\n}\n\n/* callback to initialize the contents of the MyShmem area at startup */\nstatic void\nmy_shmem_init(void *arg)\n{\n    int         tranche_id;\n\n    /* Initialize the lock */\n    tranche_id = LWLockNewTrancheId(\"my tranche name\");\n    LWLockInitialize(&MyShmem->lock, tranche_id);\n\n    ... initialize the rest of MyShmem fields ...\n}\n\n
\n

request_fn \u56de\u8c03\u4f1a\u5728\u7cfb\u7edf\u542f\u52a8\u671f\u95f4\u3001\u5171\u4eab\u5185\u5b58\u5c1a\u672a\u5206\u914d\u4e4b\u524d\u88ab\u8c03\u7528\u3002\u5b83\u5e94\u5f53\u8c03\u7528 ShmemRequestStruct() \u6765\u767b\u8bb0\u63d2\u4ef6\u7684\u5171\u4eab\u5185\u5b58\u9700\u6c42\u3002\u6ce8\u610f\uff0cShmemRequestStruct() \u5e76\u4e0d\u4f1a\u7acb\u523b\u5206\u914d\u6216\u521d\u59cb\u5316\u5185\u5b58\uff0c\u5b83\u53ea\u662f\u767b\u8bb0\u7a0d\u540e\u5728\u542f\u52a8\u5e8f\u5217\u4e2d\u8981\u5206\u914d\u7684\u7a7a\u95f4\u3002\u5185\u5b58\u5206\u914d\u5b8c\u6210\u540e\u4f1a\u88ab\u521d\u59cb\u5316\u4e3a\u96f6\u3002\u5bf9\u4e8e\u66f4\u590d\u6742\u7684\u521d\u59cb\u5316\uff0c\u53ef\u8bbe\u7f6e init_fn() \u56de\u8c03\uff1b\u8be5\u56de\u8c03\u4f1a\u5728\u5185\u5b58\u5206\u914d\u5e76\u6e05\u96f6\u4e4b\u540e\u3001\u4f46\u5728\u4efb\u4f55\u5176\u4ed6\u8fdb\u7a0b\u5f00\u59cb\u8fd0\u884c\u4e4b\u524d\u88ab\u8c03\u7528\uff0c\u56e0\u6b64\u4e0d\u9700\u8981\u52a0\u9501\u3002

\n

\u5728 Windows \u4e0a\uff0cattach_fn \u56de\u8c03\u5982\u679c\u5b58\u5728\uff0c\u8fd8\u4f1a\u5728\u6bcf\u6b21\u540e\u7aef\u542f\u52a8\u65f6\u989d\u5916\u88ab\u8c03\u7528\u3002\u5b83\u53ef\u7528\u4e8e\u521d\u59cb\u5316\u4e0e\u5171\u4eab\u5185\u5b58\u533a\u57df\u76f8\u5173\u7684\u5176\u4ed6\u6bcf\u540e\u7aef\u72b6\u6001\uff0c\u800c\u8fd9\u4e9b\u72b6\u6001\u5728\u5176\u4ed6\u7cfb\u7edf\u4e0a\u4f1a\u901a\u8fc7 fork() \u88ab\u7ee7\u627f\u3002

\n

\u5728 PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_stat_statements/pg_stat_statements.c \u91cc\u53ef\u4ee5\u627e\u5230\u4e00\u4e2a\u5206\u914d\u5171\u4eab\u5185\u5b58\u7684\u793a\u4f8b\u3002

\n
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\n
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36.10.11.2.\u00a0\u4f7f\u7528 ShmemRequestStruct \u5728\u542f\u52a8\u540e\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

\n
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\n
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\n

ShmemRequestStruct() \u4e5f\u53ef\u4ee5\u5728\u7cfb\u7edf\u542f\u52a8\u4e4b\u540e\u8c03\u7528\uff0c\u8fd9\u5bf9\u5141\u8bb8\u5728\u672a\u6307\u5b9a\u4e8eshared_preload_libraries\u4e2d\u7684\u63d2\u4ef6\u5e93\u91cc\u505a\u5c11\u91cf\u5206\u914d\u5f88\u6709\u7528\u3002\u4e0d\u8fc7\uff0c\u5728\u542f\u52a8\u4e4b\u540e\uff0c\u5982\u679c\u53ef\u7528\u5171\u4eab\u5185\u5b58\u4e0d\u8db3\uff0c\u5206\u914d\u53ef\u80fd\u4f1a\u5931\u8d25\u3002\u7cfb\u7edf\u4f1a\u4e3a\u542f\u52a8\u540e\u7684\u5206\u914d\u4fdd\u7559\u4e00\u90e8\u5206\u5185\u5b58\uff0c\u4f46\u8fd9\u4e2a\u4fdd\u7559\u91cf\u5f88\u5c0f\u3002

\n

\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c\u5728\u7cfb\u7edf\u542f\u52a8\u540e\u8c03\u7528 RegisterShmemCallbacks() \u4f1a\u62a5\u9519\u3002\u8981\u5728\u542f\u52a8\u540e\u4f7f\u7528\u5b83\uff0c\u5fc5\u987b\u5728\u4f20\u5165\u7684 ShmemCallbacks \u7ed3\u6784\u4f53\u4e2d\u8bbe\u7f6e SHMEM_CALLBACKS_ALLOW_AFTER_STARTUP \u6807\u5fd7\uff0c\u8868\u793a\u5df2\u77e5\u6653\u98ce\u9669\u3002

\n

\u5f53\u5728\u542f\u52a8\u540e\u8c03\u7528 RegisterShmemCallbacks() \u65f6\uff0c\u5b83\u4f1a\u6839\u636e\u8bf7\u6c42\u7684\u5185\u5b58\u533a\u57df\u662f\u5426\u5df2\u7ecf\u7531\u5176\u4ed6\u540e\u7aef\u521d\u59cb\u5316\u8fc7\uff0c\u7acb\u5373\u8c03\u7528\u76f8\u5e94\u7684\u56de\u8c03\u51fd\u6570\u3002\u56de\u8c03\u51fd\u6570\u4f1a\u5728\u6301\u6709\u5185\u90e8\u9501\uff08ShmemIndexLock\uff09\u7684\u60c5\u51b5\u4e0b\u6267\u884c\uff0c\u8fd9\u53ef\u4ee5\u9632\u6b62\u4e24\u4e2a\u540e\u7aef\u540c\u65f6\u5c1d\u8bd5\u521d\u59cb\u5316\u8be5\u5185\u5b58\u533a\u57df\u65f6\u51fa\u73b0\u7ade\u6001\u6761\u4ef6\u3002\u5982\u679c\u5206\u914d\u6216\u521d\u59cb\u5316\u56e0\u4efb\u4f55\u539f\u56e0\u5931\u8d25\uff0c\u8fd9\u4e9b\u5171\u4eab\u5185\u5b58\u533a\u57df\u4f1a\u5904\u4e8e\u5e9f\u5f03\u72b6\u6001\uff1b\u5728\u670d\u52a1\u5668\u91cd\u65b0\u542f\u52a8\u4e4b\u524d\uff0c\u4efb\u4f55\u9644\u52a0\u6216\u91cd\u65b0\u521d\u59cb\u5316\u8fd9\u4e9b\u533a\u57df\u7684\u5c1d\u8bd5\u90fd\u4f1a\u5931\u8d25\u3002

\n

\u540e\u7aef\u9644\u52a0\u5230\u5df2\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u533a\u57df\u65f6\uff0c\u901a\u5e38\u5fc5\u987b\u5411 ShmemRequestStruct() \u4f20\u5165\u5206\u914d\u8be5\u533a\u57df\u65f6\u4f7f\u7528\u7684\u76f8\u540c\u5927\u5c0f\uff1b\u5927\u5c0f\u4e0d\u5339\u914d\u4f1a\u62a5\u9519\u3002\u5982\u679c\u9644\u52a0\u7684\u540e\u7aef\u4e8b\u5148\u4e0d\u77e5\u9053\u5927\u5c0f\uff0c\u53ef\u4ee5\u6539\u4e3a\u4f20\u5165 SHMEM_ATTACH_UNKNOWN_SIZE\uff0c\u8df3\u8fc7\u6b64\u4ea4\u53c9\u68c0\u67e5\u3002SHMEM_ATTACH_UNKNOWN_SIZE \u53ea\u80fd\u7528\u4e8e\u9644\u52a0\u5230\u5df2\u5b58\u5728\u7684\u533a\u57df\uff1b\u5728\u5206\u914d\u533a\u57df\u4e4b\u524d\u4f7f\u7528\u5b83\u4f1a\u62a5\u9519\u3002

\n
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36.10.11.3.\u00a0\u542f\u52a8\u540e\u5206\u914d\u52a8\u6001\u5171\u4eab\u5185\u5b58

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\n
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\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u4e4b\u540e\u5b8c\u6210\u3002\u4e3a\u6b64\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8be5\u5171\u4eab\u5185\u5b58\u7684\u540e\u7aef\u90fd\u5e94\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u83b7\u53d6\u4e00\u4e2a\u6307\u9488\uff1a

\n
void *GetNamedDSMSegment(const char *name, size_t size,\n                         void (*init_callback) (void *ptr, void *arg),\n                         bool *found, void *arg)\n
\n

\u5982\u679c\u7ed9\u5b9a\u540d\u79f0\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u5c1a\u4e0d\u5b58\u5728\uff0c\u8be5\u51fd\u6570\u4f1a\u5206\u914d\u8be5\u6bb5\uff0c\u5e76\u4f7f\u7528\u63d0\u4f9b\u7684 init_callback \u56de\u8c03\u51fd\u6570\u5bf9\u5176\u8fdb\u884c\u521d\u59cb\u5316\u3002\u5982\u679c\u8be5\u6bb5\u5df2\u7ecf\u7531\u53e6\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8fc7\uff0c\u8be5\u51fd\u6570\u5c31\u53ea\u4f1a\u628a\u73b0\u6709\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u9644\u52a0\u5230\u5f53\u524d\u540e\u7aef\u3002\u5728\u524d\u4e00\u79cd\u60c5\u51b5\u4e0b\uff0cGetNamedDSMSegment \u4f1a\u628a void *arg \u53c2\u6570\u4f20\u7ed9 init_callback\u3002\u8fd9\u5bf9\u5728\u591a\u4e2a DSM \u6bb5\u4e4b\u95f4\u590d\u7528\u521d\u59cb\u5316\u56de\u8c03\u51fd\u6570\u7279\u522b\u6709\u7528\u3002

\n

GetNamedDSMSegment \u4f1a\u786e\u4fdd\u53ea\u6709\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8be5\u5185\u5b58\u6bb5\uff0c\u800c\u5176\u4ed6\u6240\u6709\u540e\u7aef\u90fd\u4f1a\u83b7\u5f97\u6307\u5411\u540c\u4e00\u5757\u5df2\u5b8c\u5168\u5206\u914d\u5e76\u521d\u59cb\u5316\u597d\u7684\u5185\u5b58\u6bb5\u7684\u6307\u9488\u3002

\n

GetNamedDSMSegment \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/test_dsm_registry/test_dsm_registry.c\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n
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36.10.12. \u8f7b\u91cf\u7ea7\u9501\uff08LWLocks\uff09

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36.10.12.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42 LWLocks

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\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLocks\u3002\u4e0e\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u4e00\u6837\uff0c\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\uff0c\u5e76\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\u3002\u6b64\u94a9\u5b50\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8fd9\u786e\u4fdd\u5b58\u5728\u4e00\u4e2a\u540d\u4e3a tranche_name\u3001\u5305\u542b num_lwlocks \u4e2a LWLocks \u7684\u6570\u7ec4\u3002\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u53d6\u5f97\u8be5\u6570\u7ec4\u7684\u6307\u9488\uff1a

\n
LWLockPadded *GetNamedLWLockTranche(const char *tranche_name)\n
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36.10.12.2.\u00a0\u542f\u52a8\u540e\u8bf7\u6c42 LWLocks

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\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u83b7\u53d6 LWLocks \u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u540e\u8fdb\u884c\uff0c\u4e5f\u65e0\u9700\u501f\u52a9 shmem_request_hook\u3002\u4e3a\u6b64\uff0c\u9996\u5148\u901a\u8fc7\u8c03\u7528\u4e0b\u9762\u7684\u51fd\u6570\u5206\u914d\u4e00\u4e2a tranche_id\uff1a

\n
int LWLockNewTrancheId(const char *name)\n
\n

\u63a5\u4e0b\u6765\uff0c\u521d\u59cb\u5316\u6bcf\u4e2a LWLock\uff0c\u5e76\u628a\u65b0\u7684 tranche_id \u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\uff1a

\n
void LWLockInitialize(LWLock *lock, int tranche_id)\n
\n

\u4e0e\u5171\u4eab\u5185\u5b58\u7c7b\u4f3c\uff0c\u6bcf\u4e2a\u540e\u7aef\u90fd\u5e94\u786e\u4fdd\u53ea\u6709\u4e00\u4e2a\u8fdb\u7a0b\u4f1a\u5206\u914d\u65b0\u7684 tranche_id \u5e76\u521d\u59cb\u5316\u6bcf\u4e00\u4e2a\u65b0\u7684 LWLock\u3002\u4e00\u79cd\u505a\u6cd5\u662f\u4ec5\u5728\u6301\u6709 AddinShmemInitLock \u72ec\u5360\u9501\u7684\u5171\u4eab\u5185\u5b58\u521d\u59cb\u5316\u4ee3\u7801\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u3002\u5982\u679c\u4f7f\u7528 GetNamedDSMSegment\uff0c\u90a3\u4e48\u5728 init_callback \u56de\u8c03\u51fd\u6570\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u5c31\u8db3\u4ee5\u907f\u514d\u7ade\u4e89\u6761\u4ef6\u3002

\n

LWLockNewTrancheId \u548c LWLockInitialize \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_prewarm/autoprewarm.c\u3002

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36.10.13. \u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6

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\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u5728\u7b49\u5f85\u4e8b\u4ef6\u7c7b\u578b Extension \u4e0b\u5b9a\u4e49\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\uff1a

\n
uint32 WaitEventExtensionNew(const char *wait_event_name)\n
\n

\u8be5\u7b49\u5f85\u4e8b\u4ef6\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u9762\u5411\u7528\u6237\u7684\u81ea\u5b9a\u4e49\u5b57\u7b26\u4e32\u3002\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/worker_spi\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n

\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\u53ef\u4ee5\u5728 pg_stat_activity \u4e2d\u67e5\u770b\uff1a

\n
=# SELECT wait_event_type, wait_event FROM pg_stat_activity\n     WHERE backend_type ~ 'worker_spi';\n wait_event_type |  wait_event\n-----------------+---------------\n Extension       | WorkerSpiMain\n(1 row)\n
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36.10.14. \u6ce8\u5165\u70b9

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\u7ed9\u5b9a\u540d\u79f0 name \u7684\u6ce8\u5165\u70b9\u53ef\u901a\u8fc7\u4ee5\u4e0b\u5b8f\u58f0\u660e\uff1a

\n
INJECTION_POINT(name, arg);\n
\n

\u670d\u52a1\u5668\u4ee3\u7801\u4e2d\u5df2\u7ecf\u5728\u82e5\u5e72\u5173\u952e\u4f4d\u7f6e\u58f0\u660e\u4e86\u6ce8\u5165\u70b9\u3002\u65b0\u589e\u6ce8\u5165\u70b9\u540e\uff0c\u9700\u8981\u91cd\u65b0\u7f16\u8bd1\u4ee3\u7801\uff0c\u624d\u80fd\u8ba9\u8be5\u6ce8\u5165\u70b9\u51fa\u73b0\u5728\u4e8c\u8fdb\u5236\u6587\u4ef6\u4e2d\u3002\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u4e5f\u53ef\u4ee5\u4f7f\u7528\u540c\u4e00\u4e2a\u5b8f\u5728\u81ea\u5df1\u7684\u4ee3\u7801\u4e2d\u58f0\u660e\u6ce8\u5165\u70b9\u3002\u6ce8\u5165\u70b9\u540d\u79f0\u5e94\u4f7f\u7528\u5c0f\u5199\u5b57\u6bcd\uff0c\u5e76\u7528\u8fde\u5b57\u7b26\u5206\u9694\u5404\u4e2a\u672f\u8bed\u3002arg \u662f\u8fd0\u884c\u65f6\u4f20\u7ed9\u56de\u8c03\u7684\u53ef\u9009\u53c2\u6570\u503c\u3002

\n

\u6267\u884c\u6ce8\u5165\u70b9\u53ef\u80fd\u9700\u8981\u5206\u914d\u5c11\u91cf\u5185\u5b58\uff0c\u800c\u8fd9\u53ef\u80fd\u5931\u8d25\u3002\u5982\u679c\u4f60\u9700\u8981\u5728\u4e00\u4e2a\u4e0d\u5141\u8bb8\u52a8\u6001\u5206\u914d\u7684\u4e34\u754c\u533a\u4e2d\u4f7f\u7528\u6ce8\u5165\u70b9\uff0c\u53ef\u4ee5\u91c7\u7528\u4ee5\u4e0b\u4e24\u6b65\u6cd5\uff1a

\n
INJECTION_POINT_LOAD(name);\nINJECTION_POINT_CACHED(name, arg);\n
\n

\u5728\u8fdb\u5165\u4e34\u754c\u533a\u4e4b\u524d\uff0c\u8c03\u7528 INJECTION_POINT_LOAD\u3002\u5b83\u4f1a\u68c0\u67e5\u5171\u4eab\u5185\u5b58\u72b6\u6001\uff0c\u5e76\u5728\u8be5\u6ce8\u5165\u70b9\u5904\u4e8e\u6fc0\u6d3b\u72b6\u6001\u65f6\u628a\u56de\u8c03\u52a0\u8f7d\u5230\u540e\u7aef\u79c1\u6709\u5185\u5b58\u4e2d\u3002\u5728\u4e34\u754c\u533a\u5185\u90e8\uff0c\u518d\u7528 INJECTION_POINT_CACHED \u6765\u6267\u884c\u56de\u8c03\u3002

\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u4e3a\u4e00\u4e2a\u5df2\u7ecf\u58f0\u660e\u597d\u7684\u6ce8\u5165\u70b9\u9644\u52a0\u56de\u8c03\uff1a

\n
extern void InjectionPointAttach(const char *name,\n                                 const char *library,\n                                 const char *function,\n                                 const void *private_data,\n                                 int private_data_size);\n
\n

name \u662f\u6ce8\u5165\u70b9\u7684\u540d\u79f0\uff1b\u6267\u884c\u5230\u8fbe\u6b64\u6ce8\u5165\u70b9\u65f6\uff0c\u5c06\u6267\u884c\u4ece library \u52a0\u8f7d\u7684\u51fd\u6570\u3002private_data \u662f\u4e00\u5757\u5927\u5c0f\u4e3a private_data_size \u7684\u79c1\u6709\u6570\u636e\u533a\u57df\uff0c\u5728\u6267\u884c\u56de\u8c03\u65f6\u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\u3002

\n

\u4e0b\u9762\u662f\u4e00\u4e2a InjectionPointCallback \u7684\u793a\u4f8b\uff1a

\n
static void\ncustom_injection_callback(const char *name,\n                          const void *private_data,\n                          void *arg)\n{\n    uint32 wait_event_info = WaitEventInjectionPointNew(name);\n\n    pgstat_report_wait_start(wait_event_info);\n    elog(NOTICE, \"%s: executed custom callback\", name);\n    pgstat_report_wait_end();\n}\n
\n

\u8fd9\u4e2a\u56de\u8c03\u4f1a\u4ee5 NOTICE \u7ea7\u522b\u5411\u670d\u52a1\u5668\u9519\u8bef\u65e5\u5fd7\u5199\u5165\u4e00\u6761\u6d88\u606f\uff0c\u4f46\u56de\u8c03\u5b8c\u5168\u53ef\u4ee5\u5b9e\u73b0\u66f4\u590d\u6742\u7684\u903b\u8f91\u3002

\n

\u53e6\u4e00\u79cd\u5b9a\u4e49\u201c\u5230\u8fbe\u6ce8\u5165\u70b9\u65f6\u5e94\u6267\u884c\u4ec0\u4e48\u52a8\u4f5c\u201d\u7684\u65b9\u5f0f\uff0c\u662f\u628a\u6d4b\u8bd5\u4ee3\u7801\u76f4\u63a5\u5199\u5728\u5e38\u89c4\u6e90\u4ee3\u7801\u65c1\u8fb9\u3002\u5982\u679c\u8be5\u52a8\u4f5c\u4f9d\u8d56\u4e8e\u52a0\u8f7d\u6a21\u5757\u65e0\u6cd5\u8bbf\u95ee\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u8fd9\u4f1a\u5f88\u6709\u7528\u3002\u6b64\u65f6\u53ef\u4ee5\u4f7f\u7528 IS_INJECTION_POINT_ATTACHED \u5b8f\u6765\u68c0\u67e5\u67d0\u4e2a\u6ce8\u5165\u70b9\u662f\u5426\u5df2\u9644\u52a0\uff0c\u4f8b\u5982\uff1a

\n
#ifdef USE_INJECTION_POINTS\nif (IS_INJECTION_POINT_ATTACHED(\"before-foobar\"))\n{\n    /* change a local variable if injection point is attached */\n    local_var = 123;\n\n    /* also execute the callback */\n    INJECTION_POINT_CACHED(\"before-foobar\", NULL);\n}\n#endif\n
\n

\u6ce8\u610f\uff0c\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u4e0a\u7684\u56de\u8c03\u4e0d\u4f1a\u7531 IS_INJECTION_POINT_ATTACHED \u5b8f\u6267\u884c\u3002\u5982\u679c\u4f60\u60f3\u6267\u884c\u8be5\u56de\u8c03\uff0c\u5c31\u5fc5\u987b\u50cf\u4e0a\u9762\u7684\u793a\u4f8b\u90a3\u6837\u53e6\u5916\u8c03\u7528 INJECTION_POINT_CACHED\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e5f\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u89e3\u9664\u4e00\u4e2a\u6ce8\u5165\u70b9\uff1a

\n
extern bool InjectionPointDetach(const char *name);\n
\n

\u6210\u529f\u65f6\u8fd4\u56de true\uff0c\u5426\u5219\u8fd4\u56de false\u3002

\n

\u4e00\u4e2a\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u7684\u56de\u8c03\u4f1a\u5728\u6240\u6709\u540e\u7aef\u4e2d\u751f\u6548\uff0c\u5305\u62ec\u5728\u8c03\u7528 InjectionPointAttach \u4e4b\u540e\u624d\u542f\u52a8\u7684\u540e\u7aef\u3002\u5b83\u4f1a\u4e00\u76f4\u4fdd\u6301\u9644\u52a0\u72b6\u6001\uff0c\u76f4\u5230\u670d\u52a1\u5668\u505c\u6b62\uff0c\u6216\u8005\u901a\u8fc7 InjectionPointDetach \u5c06\u5176\u89e3\u9664\u3002

\n

\u76f8\u5173\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 src/test/modules/injection_points\u3002

\n

\u8981\u542f\u7528\u6ce8\u5165\u70b9\uff0c\u4f7f\u7528 configure \u65f6\u9700\u6307\u5b9a --enable-injection-points\uff0c\u4f7f\u7528 Meson \u65f6\u9700\u6307\u5b9a -Dinjection_points=true\u3002

\n
\n
\n
\n
\n
\n

36.10.15. \u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1

\n
\n
\n
\n

\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u53ef\u4ee5\u4f7f\u7528\u5728\u7d2f\u8ba1\u7edf\u8ba1\u7cfb\u7edf\u4e2d\u6ce8\u518c\u7684\u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1\u7c7b\u578b\u3002

\n

\u9996\u5148\uff0c\u5b9a\u4e49\u4e00\u4e2a PgStat_KindInfo\uff0c\u5176\u4e2d\u5305\u542b\u4e0e\u6240\u6ce8\u518c\u81ea\u5b9a\u4e49\u7c7b\u578b\u76f8\u5173\u7684\u5168\u90e8\u4fe1\u606f\u3002\u4f8b\u5982\uff1a

\n
static const PgStat_KindInfo custom_stats = {\n    .name = \"custom_stats\",\n    .fixed_amount = false,\n    .shared_size = sizeof(PgStatShared_Custom),\n    .shared_data_off = offsetof(PgStatShared_Custom, stats),\n    .shared_data_len = sizeof(((PgStatShared_Custom *) 0)->stats),\n    .pending_size = sizeof(PgStat_StatCustomEntry),\n}\n
\n

\u7136\u540e\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8fd9\u79cd\u81ea\u5b9a\u4e49\u7c7b\u578b\u7684\u540e\u7aef\uff0c\u90fd\u9700\u8981\u4f7f\u7528 pgstat_register_kind \u6ce8\u518c\u5b83\uff0c\u5e76\u6307\u5b9a\u4e00\u4e2a\u7528\u4e8e\u5b58\u50a8\u8be5\u7c7b\u7edf\u8ba1\u6761\u76ee\u7684\u552f\u4e00 ID\uff1a

\n
extern PgStat_Kind pgstat_register_kind(PgStat_Kind kind,\n                                        const PgStat_KindInfo *kind_info);\n
\n

\u5728\u5f00\u53d1\u65b0\u6269\u5c55\u65f6\uff0c\u5e94\u5c06 PGSTAT_KIND_EXPERIMENTAL \u7528\u4f5c kind\u3002\u5f53\u4f60\u51c6\u5907\u628a\u6269\u5c55\u53d1\u5e03\u7ed9\u7528\u6237\u65f6\uff0c\u8bf7\u5728 Custom Cumulative Statistics \u9875\u9762\u4e0a\u9884\u7559\u4e00\u4e2a kind ID\u3002

\n

\u5173\u4e8e PgStat_KindInfo API \u7684\u7ec6\u8282\uff0c\u53ef\u89c1 src/include/utils/pgstat_internal.h\u3002

\n

\u5df2\u6ce8\u518c\u7684\u7edf\u8ba1\u7c7b\u578b\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u540d\u79f0\u4ee5\u53ca\u4e00\u4e2a\u5728\u5171\u4eab\u5185\u5b58\u4e2d\u4f9b\u6574\u4e2a\u670d\u52a1\u5668\u5171\u4eab\u7684\u552f\u4e00 ID\u3002\u6bcf\u4e2a\u4f7f\u7528\u81ea\u5b9a\u4e49\u7edf\u8ba1\u7c7b\u578b\u7684\u540e\u7aef\u90fd\u4f1a\u7ef4\u62a4\u4e00\u4e2a\u672c\u5730\u7f13\u5b58\uff0c\u7528\u6765\u4fdd\u5b58\u5404\u4e2a\u81ea\u5b9a\u4e49 PgStat_KindInfo \u7684\u4fe1\u606f\u3002

\n

\u5e94\u5c06\u5b9e\u73b0\u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1\u7c7b\u578b\u7684\u6269\u5c55\u6a21\u5757\u52a0\u5165shared_preload_libraries\uff0c\u4ee5\u4fbf\u5728 PostgreSQL \u542f\u52a8\u671f\u95f4\u5c3d\u65e9\u8f7d\u5165\u3002

\n

\u5c55\u793a\u5982\u4f55\u6ce8\u518c\u5e76\u4f7f\u7528\u81ea\u5b9a\u4e49\u7edf\u8ba1\u4fe1\u606f\u7684\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/test_custom_stats\u3002

\n
\n
\n
\n
\n
\n

36.10.16. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern \"C\" \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern \"C\"\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern \"C\"\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

\n
\n
", "manual_path": "/docs/19/xfunc-c.html", "localization": {"status": "complete", "sources": [{"url": "/docs/19/protocol-overview.html", "method": "same-major semantic node", "sha256": "4650a5af6514ccd289c59f90ba62490b00e797ee04c02359ef9e2174c1f276ed", "language": "zh", "matched_nodes": ["#PROTOCOL-OVERVIEW/div[9]/p[1]/span[2]/span[0]"]}, {"url": "/docs/19/xfunc-c.html", "method": "same-major semantic node", "sha256": "280b87b6c75df1c65f4fa4342c909e5e22ef756458232ac785459c8176101153", "language": "zh", "matched_nodes": ["#XFUNC-C/div[0]", "#XFUNC-C/div[10]/div[2]/div[0]", "#XFUNC-C/div[10]/div[2]/p[2]", "#XFUNC-C/div[10]/div[3]/div[0]", "#XFUNC-C/div[10]/div[3]/div[2]/p[1]", "#XFUNC-C/div[10]/div[3]/div[3]/p[1]", "#XFUNC-C/div[10]/div[3]/div[3]/p[2]", "#XFUNC-C/div[10]/div[4]/div[0]", "#XFUNC-C/div[10]/div[4]/div[2]/p[1]", "#XFUNC-C/div[10]/div[4]/div[3]/p[1]", "#XFUNC-C/div[10]/div[4]/div[3]/p[2]", "#XFUNC-C/div[10]/div[4]/div[3]/p[3]", "#XFUNC-C/div[10]/div[4]/div[3]/p[4]", 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"#XFUNC-C/div[18]/p[15]", "#XFUNC-C/div[18]/p[16]", "#XFUNC-C/div[18]/p[18]", "#XFUNC-C/div[18]/p[19]", "#XFUNC-C/div[18]/p[1]", "#XFUNC-C/div[18]/p[20]", "#XFUNC-C/div[18]/p[3]", "#XFUNC-C/div[18]/p[4]", "#XFUNC-C/div[18]/p[6]", "#XFUNC-C/div[18]/p[7]", "#XFUNC-C/div[19]/p[10]", "#XFUNC-C/div[19]/p[1]", "#XFUNC-C/div[19]/p[2]", "#XFUNC-C/div[19]/p[4]", "#XFUNC-C/div[19]/p[6]", "#XFUNC-C/div[19]/p[7]", "#XFUNC-C/div[19]/p[8]", "#XFUNC-C/div[19]/p[9]", "#XFUNC-C/div[1]/dl[0]/dt[0]", "#XFUNC-C/div[1]/dl[0]/dt[10]", "#XFUNC-C/div[1]/dl[0]/dt[12]", "#XFUNC-C/div[1]/dl[0]/dt[13]", "#XFUNC-C/div[1]/dl[0]/dt[14]", "#XFUNC-C/div[1]/dl[0]/dt[15]", "#XFUNC-C/div[1]/dl[0]/dt[1]", "#XFUNC-C/div[1]/dl[0]/dt[2]", "#XFUNC-C/div[1]/dl[0]/dt[3]", "#XFUNC-C/div[1]/dl[0]/dt[4]", "#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[20]/div[3]/ul[0]/li[0]", 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"manual_html": "
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36.10.\u00a0C \u8bed\u8a00\u51fd\u6570

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\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

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\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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36.10.1. \u52a8\u6001\u8f7d\u5165

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\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

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\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

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\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

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\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

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\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u904d\u5386\u901a\u5f80\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u6216\u8005

\n
PG_MODULE_MAGIC_EXT(parameters);\n
\n

PG_MODULE_MAGIC_EXT \u8fd9\u79cd\u5f62\u5f0f\u5141\u8bb8\u4e3a\u6a21\u5757\u6307\u5b9a\u9644\u52a0\u4fe1\u606f\uff1b\u76ee\u524d\u53ef\u4ee5\u6dfb\u52a0\u540d\u79f0\u548c/\u6216\u7248\u672c\u5b57\u7b26\u4e32\u3002\uff08\u5c06\u6765\u53ef\u80fd\u5141\u8bb8\u66f4\u591a\u5b57\u6bb5\u3002\uff09\u53ef\u4ee5\u5199\u6210\u8fd9\u6837\uff1a

\n
PG_MODULE_MAGIC_EXT(\n    .name = \"my_module_name\",\n    .version = \"1.2.3\"\n);\n
\n

\u4e4b\u540e\uff0c\u540d\u79f0\u548c\u7248\u672c\u53ef\u4ee5\u901a\u8fc7 pg_get_loaded_modules() \u51fd\u6570\u67e5\u770b\u3002\u7248\u672c\u5b57\u7b26\u4e32\u7684\u5177\u4f53\u542b\u4e49\u4e0d\u53d7 PostgreSQL \u9650\u5236\uff0c\u4f46\u5efa\u8bae\u91c7\u7528\u8bed\u4e49\u5316\u7248\u672c\u89c4\u5219\u3002

\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u5305\u542b\u4e00\u4e2a\u521d\u59cb\u5316\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init\u7684\u51fd\u6570\uff0c\u90a3\u4e2a\u51fd\u6570\u5c06\u5728\u52a0\u8f7d\u6587\u4ef6\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u4efb\u4f55\u53c2\u6570\uff0c\u5e94\u8be5\u8fd4\u56devoid\u3002\u76ee\u524d\u6ca1\u6709\u529e\u6cd5\u5378\u8f7d\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u3002

\n
\n
\n
\n
\n
\n

36.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u5c06\u5b83\u4eec\u4f20\u5165\u51fd\u6570\u548c\u4ece\u51fd\u6570\u4f20\u51fa\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012\u30014 \u6216 8 \u5b57\u8282\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a036.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a036.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u51fd\u6570\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a036.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a036.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
\u6587\u672ctext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u8981\u8c03\u7528\u53e6\u4e00\u4e2a\u7248\u672c-1 \u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528 DirectFunctionCalln(func, arg1, ..., argn)\u3002\u8fd9\u5728\u4f60\u60f3\u8c03\u7528\u6807\u51c6\u5185\u90e8\u5e93\u4e2d\u5b9a\u4e49\u7684\u51fd\u6570\u65f6\u5c24\u5176\u6709\u7528\uff0c\u56e0\u4e3a\u5b83\u63d0\u4f9b\u4e86\u4e0e\u5176 SQL \u7b7e\u540d\u76f8\u4f3c\u7684\u63a5\u53e3\u3002

\n

\u8fd9\u4e9b\u4fbf\u5229\u51fd\u6570\u4ee5\u53ca\u7c7b\u4f3c\u51fd\u6570\u90fd\u53ef\u4ee5\u5728 fmgr.h \u4e2d\u627e\u5230\u3002DirectFunctionCalln \u7cfb\u5217\u628a C \u51fd\u6570\u540d\u4f5c\u4e3a\u5176\u7b2c\u4e00\u4e2a\u53c2\u6570\u3002\u53e6\u6709 OidFunctionCalln \u7b49\u4e00\u4e9b\u53d8\u4f53\uff0c\u5b83\u4eec\u63a5\u6536\u76ee\u6807\u51fd\u6570\u7684 OID\u3002\u6240\u6709\u8fd9\u4e9b\u51fd\u6570\u90fd\u8981\u6c42\u4ee5 Datum \u5f62\u5f0f\u63d0\u4f9b\u51fd\u6570\u53c2\u6570\uff0c\u8fd4\u56de\u503c\u4e5f\u540c\u6837\u662f Datum\u3002\u6ce8\u610f\uff0c\u4f7f\u7528\u8fd9\u4e9b\u4fbf\u5229\u51fd\u6570\u65f6\uff0c\u53c2\u6570\u548c\u7ed3\u679c\u90fd\u4e0d\u80fd\u4e3a NULL\u3002

\n

\u4f8b\u5982\uff0c\u8981\u5728 C \u4e2d\u8c03\u7528 starts_with(text, text)\uff0c\u4f60\u53ef\u4ee5\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\u67e5\u5230\u5b83\u7684 C \u5b9e\u73b0\u662f Datum text_starts_with(PG_FUNCTION_ARGS) \u51fd\u6570\u3002\u901a\u5e38\u4f60\u4f1a\u7528 DirectFunctionCall2(text_starts_with, ...) \u6765\u8c03\u7528\u5b83\u3002\u4e0d\u8fc7\uff0cstarts_with(text, text) \u9700\u8981\u6392\u5e8f\u89c4\u5219\u4fe1\u606f\uff0c\u56e0\u6b64\u5982\u679c\u8fd9\u6837\u8c03\u7528\uff0c\u4f1a\u56e0\u201c\u65e0\u6cd5\u786e\u5b9a\u5b57\u7b26\u4e32\u6bd4\u8f83\u8be5\u4f7f\u7528\u54ea\u4e00\u79cd\u6392\u5e8f\u89c4\u5219\u201d\u800c\u5931\u8d25\u3002\u4f60\u5fc5\u987b\u6539\u7528 DirectFunctionCall2Coll(text_starts_with, ...)\uff0c\u5e76\u63d0\u4f9b\u6240\u9700\u7684\u6392\u5e8f\u89c4\u5219\uff0c\u901a\u5e38\u5c31\u662f\u4ece PG_GET_COLLATION() \u4f20\u9012\u8fdb\u6765\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u6240\u793a\u3002

\n

fmgr.h \u8fd8\u63d0\u4f9b\u4e86\u4fbf\u4e8e\u5728 C \u7c7b\u578b\u548c Datum \u4e4b\u95f4\u8f6c\u6362\u7684\u5b8f\u3002\u4f8b\u5982\uff0c\u8981\u628a Datum \u8f6c\u6210 text*\uff0c\u53ef\u4ee5\u4f7f\u7528 DatumGetTextPP(X)\u3002\u867d\u7136\u67d0\u4e9b\u7c7b\u578b\u4e3a\u53cd\u5411\u8f6c\u6362\u63d0\u4f9b\u4e86\u540d\u4e3a TypeGetDatum(X) \u4e4b\u7c7b\u7684\u5b8f\uff0c\u4f46 text* \u6ca1\u6709\uff1b\u5bf9\u5b83\u800c\u8a00\uff0c\u76f4\u63a5\u4f7f\u7528\u901a\u7528\u5b8f PointerGetDatum(X) \u5373\u53ef\u3002\u5982\u679c\u4f60\u7684\u6269\u5c55\u5b9a\u4e49\u4e86\u989d\u5916\u7684\u7c7b\u578b\uff0c\u901a\u5e38\u4e5f\u5f88\u65b9\u4fbf\u4e3a\u8fd9\u4e9b\u7c7b\u578b\u5b9a\u4e49\u7c7b\u4f3c\u7684\u5b8f\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n#include \"varatt.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = palloc_object(Point);\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy(VARDATA(new_t),          /* destination */\n           VARDATA_ANY(t),          /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n/* A wrapper around starts_with(text, text) */\n\nPG_FUNCTION_INFO_V1(t_starts_with);\n\nDatum\nt_starts_with(PG_FUNCTION_ARGS)\n{\n    text       *t1 = PG_GETARG_TEXT_PP(0);\n    text       *t2 = PG_GETARG_TEXT_PP(1);\n    Oid         collid = PG_GET_COLLATION();\n    bool        result;\n\n    result = DatumGetBool(DirectFunctionCall2Coll(text_starts_with,\n                                                  collid,\n                                                  PointerGetDatum(t1),\n                                                  PointerGetDatum(t2)));\n    PG_RETURN_BOOL(result);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION t_starts_with(text, text) RETURNS boolean\n     AS 'DIRECTORY/funcs', 't_starts_with'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u5f92\u589e\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a036.10.9\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a037\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a057\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

\n
\n
\n
\n
\n
\n

36.10.4. \u7f16\u5199\u4ee3\u7801

\n
\n
\n
\n

\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

\n

\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

\n
\n
    \n
  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a036.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

    \n
    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

    \n
    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

36.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

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FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 13.0 \u8d77\u9002\u7528\uff1b\u66f4\u65e9\u7248\u672c\u4f7f\u7528\u7684\u662f gcc \u7f16\u8bd1\u5668\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f GCC \u7684 -fPIC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u7f16\u8bd1\u5668\u9009\u9879\u662f GCC \u7684 -shared\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

36.10.6. \u670d\u52a1\u5668 API \u548c ABI \u7a33\u5b9a\u6027\u6307\u5357

\n
\n
\n
\n

\u672c\u8282\u5411\u6269\u5c55\u548c\u5176\u4ed6\u670d\u52a1\u5668\u63d2\u4ef6\u7684\u4f5c\u8005\u63d0\u4f9b\u6709\u5173 PostgreSQL \u670d\u52a1\u5668 API \u4e0e ABI \u7a33\u5b9a\u6027\u7684\u6307\u5bfc\u3002

\n
\n
\n
\n
\n

\n
\n
\n

36.10.6.1.\u00a0\u6982\u8ff0

\n
\n
\n

\n
\n
\n
\n

PostgreSQL \u670d\u52a1\u5668\u4e3a\u63d2\u4ef6\u63d0\u4f9b\u4e86\u591a\u4e2a\u8fb9\u754c\u6e05\u6670\u7684 API\uff0c\u4f8b\u5982\u672c\u7ae0\u4ecb\u7ecd\u7684\u51fd\u6570\u7ba1\u7406\u5668 fmgr\u3001SPI\uff08\u7b2c 45 \u7ae0\uff09\u4ee5\u53ca\u4e13\u4e3a\u6269\u5c55\u8bbe\u8ba1\u7684\u5404\u79cd\u94a9\u5b50\u3002\u8fd9\u4e9b\u63a5\u53e3\u7ecf\u8fc7\u8c28\u614e\u7ef4\u62a4\uff0c\u4ee5\u4fdd\u6301\u957f\u671f\u7a33\u5b9a\u6027\u548c\u517c\u5bb9\u6027\u3002\u4e0d\u8fc7\uff0c\u670d\u52a1\u5668\u4e2d\u5168\u90e8\u5168\u5c40\u51fd\u6570\u548c\u53d8\u91cf\u5b9e\u9645\u4e0a\u90fd\u6784\u6210\u4e86\u53ef\u516c\u5f00\u4f7f\u7528\u7684 API\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u5728\u8bbe\u8ba1\u65f6\u5e76\u672a\u8003\u8651\u53ef\u6269\u5c55\u6027\u548c\u957f\u671f\u7a33\u5b9a\u6027\u3002

\n

\u56e0\u6b64\uff0c\u867d\u7136\u4f7f\u7528\u8fd9\u4e9b\u63a5\u53e3\u662f\u5b8c\u5168\u5141\u8bb8\u7684\uff0c\u4f46\u8d8a\u662f\u504f\u79bb\u90a3\u4e9b\u4e45\u7ecf\u5b9e\u8df5\u8003\u9a8c\u7684\u8def\u5f84\uff0c\u5c06\u6765\u9047\u5230 API \u6216 ABI \u517c\u5bb9\u6027\u95ee\u9898\u7684\u53ef\u80fd\u6027\u5c31\u8d8a\u5927\u3002\u9f13\u52b1\u6269\u5c55\u4f5c\u8005\u53cd\u9988\u81ea\u5df1\u7684\u9700\u6c42\uff0c\u4ee5\u4fbf\u968f\u7740\u65f6\u95f4\u63a8\u79fb\u548c\u65b0\u7528\u6cd5\u7684\u51fa\u73b0\uff0c\u67d0\u4e9b\u63a5\u53e3\u80fd\u591f\u88ab\u89c6\u4e3a\u66f4\u7a33\u5b9a\uff0c\u6216\u8005\u53ef\u4ee5\u52a0\u5165\u65b0\u7684\u3001\u8bbe\u8ba1\u66f4\u5b8c\u5584\u7684\u63a5\u53e3\u3002

\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.6.2.\u00a0API \u517c\u5bb9\u6027

\n
\n
\n

\n
\n
\n
\n

API\uff0c\u5373\u5e94\u7528\u7a0b\u5e8f\u7f16\u7a0b\u63a5\u53e3\uff0c\u662f\u7f16\u8bd1\u65f6\u4f7f\u7528\u7684\u63a5\u53e3\u3002

\n
\n
\n
\n
\n
36.10.6.2.1.\u00a0Major Versions
\n
\n
\n
\n

\u5728 PostgreSQL \u4e0d\u540c\u4e3b\u7248\u672c\u4e4b\u95f4\uff0c\u4e0d\u627f\u8bfa API \u517c\u5bb9\u6027\u3002\u56e0\u6b64\uff0c\u6269\u5c55\u4ee3\u7801\u53ef\u80fd\u9700\u8981\u4fee\u6539\u6e90\u4ee3\u7801\u624d\u80fd\u540c\u65f6\u652f\u6301\u591a\u4e2a\u4e3b\u7248\u672c\u3002\u8fd9\u7c7b\u5dee\u5f02\u901a\u5e38\u53ef\u4ee5\u901a\u8fc7\u9884\u5904\u7406\u5668\u6761\u4ef6\uff08\u4f8b\u5982 #if PG_VERSION_NUM >= 160000\uff09\u6765\u7ba1\u7406\u3002\u90a3\u4e9b\u4f7f\u7528\u4e86\u8fb9\u754c\u6e05\u6670\u63a5\u53e3\u4e4b\u5916\u80fd\u529b\u7684\u590d\u6742\u6269\u5c55\uff0c\u901a\u5e38\u6bcf\u4e2a\u670d\u52a1\u5668\u4e3b\u7248\u672c\u90fd\u9700\u8981\u505a\u5c11\u91cf\u8fd9\u7c7b\u4fee\u6539\u3002

\n
\n
\n
\n
\n
\n
36.10.6.2.2.\u00a0Minor Versions
\n
\n
\n
\n

PostgreSQL \u4f1a\u5c3d\u529b\u907f\u514d\u5728\u5c0f\u7248\u672c\u53d1\u5e03\u4e2d\u7834\u574f\u670d\u52a1\u5668 API\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u80fd\u9488\u5bf9\u67d0\u4e2a\u5c0f\u7248\u672c\u7f16\u8bd1\u5e76\u6b63\u5e38\u5de5\u4f5c\u7684\u6269\u5c55\u4ee3\u7801\uff0c\u4e5f\u5e94\u5f53\u80fd\u591f\u9488\u5bf9\u540c\u4e00\u4e3b\u7248\u672c\u7684\u5176\u4ed6\u4efb\u610f\u5c0f\u7248\u672c\uff08\u65e0\u8bba\u8fc7\u53bb\u8fd8\u662f\u5c06\u6765\uff09\u7f16\u8bd1\u5e76\u6b63\u5e38\u5de5\u4f5c\u3002

\n

\u5982\u679c\u786e\u5b9e\u9700\u8981\u505a\u51fa\u53d8\u66f4\uff0c\u4e5f\u4f1a\u5728\u8003\u8651\u6269\u5c55\u9700\u6c42\u7684\u524d\u63d0\u4e0b\u8c28\u614e\u7ba1\u7406\u3002\u8fd9\u7c7b\u53d8\u66f4\u4f1a\u5728\u53d1\u5e03\u8bf4\u660e\uff08\u9644\u5f55\u00a0E\uff09\u4e2d\u8fdb\u884c\u8bf4\u660e\u3002

\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.6.3.\u00a0ABI \u517c\u5bb9\u6027

\n
\n
\n

\n
\n
\n
\n

ABI\uff0c\u5373\u5e94\u7528\u7a0b\u5e8f\u4e8c\u8fdb\u5236\u63a5\u53e3\uff0c\u662f\u8fd0\u884c\u65f6\u4f7f\u7528\u7684\u63a5\u53e3\u3002

\n
\n
\n
\n
\n
36.10.6.3.1.\u00a0Major Versions
\n
\n
\n
\n

\u4e0d\u540c\u4e3b\u7248\u672c\u7684\u670d\u52a1\u5668\u5728 ABI \u4e0a\u662f\u6709\u610f\u4e0d\u517c\u5bb9\u7684\u3002\u56e0\u6b64\uff0c\u4f7f\u7528\u670d\u52a1\u5668 API \u7684\u6269\u5c55\u5fc5\u987b\u9488\u5bf9\u6bcf\u4e00\u4e2a\u4e3b\u7248\u672c\u91cd\u65b0\u7f16\u8bd1\u3002\u5305\u542b PG_MODULE_MAGIC\uff08\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\uff09\u53ef\u4ee5\u786e\u4fdd\u9488\u5bf9\u67d0\u4e2a\u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u4ee3\u7801\u4f1a\u88ab\u5176\u4ed6\u4e3b\u7248\u672c\u62d2\u7edd\u3002

\n
\n
\n
\n
\n
\n
36.10.6.3.2.\u00a0Minor Versions
\n
\n
\n
\n

PostgreSQL \u4f1a\u5c3d\u529b\u907f\u514d\u5728\u5c0f\u7248\u672c\u53d1\u5e03\u4e2d\u7834\u574f\u670d\u52a1\u5668 ABI\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u9488\u5bf9\u4efb\u610f\u4e00\u4e2a\u5c0f\u7248\u672c\u7f16\u8bd1\u7684\u6269\u5c55\uff0c\u5e94\u5f53\u80fd\u4e0e\u540c\u4e00\u4e3b\u7248\u672c\u8fc7\u53bb\u6216\u5c06\u6765\u7684\u5176\u4ed6\u4efb\u610f\u5c0f\u7248\u672c\u4e00\u8d77\u5de5\u4f5c\u3002

\n

\u5982\u679c\u786e\u5b9e\u9700\u8981\u53d8\u66f4\uff0cPostgreSQL \u4f1a\u5c3d\u91cf\u9009\u62e9\u4fb5\u5165\u6027\u6700\u5c0f\u7684\u65b9\u5f0f\uff0c\u4f8b\u5982\u628a\u65b0\u5b57\u6bb5\u585e\u8fdb\u586b\u5145\u7a7a\u95f4\uff0c\u6216\u8005\u9644\u52a0\u5230\u7ed3\u6784\u4f53\u672b\u5c3e\u3002\u8fd9\u7c7b\u4fee\u6539\u901a\u5e38\u4e0d\u5e94\u5f71\u54cd\u6269\u5c55\uff0c\u9664\u975e\u6269\u5c55\u4f7f\u7528\u4e86\u975e\u5e38\u4e0d\u5bfb\u5e38\u7684\u4ee3\u7801\u6a21\u5f0f\u3002

\n

\u7136\u800c\uff0c\u5728\u6781\u5c11\u6570\u60c5\u51b5\u4e0b\uff0c\u5373\u4f7f\u662f\u8fd9\u79cd\u975e\u4fb5\u5165\u5f0f\u53d8\u66f4\u4e5f\u53ef\u80fd\u4e0d\u73b0\u5b9e\u751a\u81f3\u4e0d\u53ef\u80fd\u505a\u5230\u3002\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\u65f6\uff0c\u4e5f\u4f1a\u5728\u8003\u8651\u6269\u5c55\u9700\u6c42\u7684\u524d\u63d0\u4e0b\u8c28\u614e\u7ba1\u7406\u8be5\u53d8\u66f4\u3002\u8fd9\u7c7b\u53d8\u66f4\u540c\u6837\u4f1a\u8bb0\u5f55\u5728\u53d1\u5e03\u8bf4\u660e\uff08\u9644\u5f55\u00a0E\uff09\u4e2d\u3002

\n

\u4f46\u8bf7\u6ce8\u610f\uff0c\u670d\u52a1\u5668\u4e2d\u6709\u5f88\u591a\u90e8\u5206\u5e76\u4e0d\u662f\u4f5c\u4e3a\u53ef\u516c\u5f00\u4f7f\u7528\u7684 API \u6765\u8bbe\u8ba1\u548c\u7ef4\u62a4\u7684\uff08\u800c\u4e14\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u5176\u771f\u5b9e\u8fb9\u754c\u4e5f\u5e76\u4e0d\u6e05\u6670\uff09\u3002\u5982\u679c\u51fa\u73b0\u7d27\u6025\u9700\u6c42\uff0c\u5bf9\u8fd9\u4e9b\u90e8\u5206\u8fdb\u884c\u4fee\u6539\u65f6\uff0c\u81ea\u7136\u4f1a\u6bd4\u4fee\u6539\u90a3\u4e9b\u8fb9\u754c\u6e05\u695a\u4e14\u5e7f\u6cdb\u4f7f\u7528\u7684\u63a5\u53e3\u65f6\u66f4\u5c11\u8003\u8651\u6269\u5c55\u4ee3\u7801\u7684\u517c\u5bb9\u6027\u3002

\n

\u6b64\u5916\uff0c\u5728\u7f3a\u4e4f\u81ea\u52a8\u5316\u68c0\u6d4b\u8fd9\u7c7b\u53d8\u5316\u7684\u673a\u5236\u65f6\uff0c\u8fd9\u5e76\u4e0d\u80fd\u6784\u6210\u4e25\u683c\u4fdd\u8bc1\uff1b\u4e0d\u8fc7\u4ece\u5386\u53f2\u4e0a\u770b\uff0c\u8fd9\u79cd\u7834\u574f\u6027\u53d8\u5316\u6781\u4e3a\u7f55\u89c1\u3002

\n
\n
\n
\n
\n
\n
\n
\n

36.10.7. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u51fd\u6570\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

36.10.8. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.9. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff08\u5305\u62ec\u7b2c\u4e00\u6b21\uff09\uff0c\u90fd\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_INT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = palloc_array(char *, 3);\n        values[0] = palloc_array(char, 16);\n        values[1] = palloc_array(char, 16);\n        values[2] = palloc_array(char, 16);\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
\n
\n
\n
\n
\n

36.10.10. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a036.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

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36.10.11. \u5171\u4eab\u5185\u5b58

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36.10.11.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

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\u63d2\u4ef6\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u3002\u8981\u505a\u5230\u8fd9\u4e00\u70b9\uff0c\u63d2\u4ef6\u7684\u5171\u4eab\u5e93\u5fc5\u987b\u901a\u8fc7shared_preload_libraries\u9884\u52a0\u8f7d\u3002\u8be5\u5171\u4eab\u5e93\u8fd8\u5e94\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c\u56de\u8c03\uff0c\u4ee5\u4fbf\u5728\u7cfb\u7edf\u542f\u52a8\u7684\u5408\u9002\u9636\u6bb5\u521d\u59cb\u5316\u5171\u4eab\u5185\u5b58\u3002\u793a\u4f8b\u5982\u4e0b\uff1a

\n
typedef struct MyShmemData {\n    LWLock      lock;    /* protects the fields below */\n\n    ... shared memory contents ...\n} MyShmemData;\n\nstatic MyShmemData *MyShmem;    /* pointer to the struct in shared memory */\n\nstatic void my_shmem_request(void *arg);\nstatic void my_shmem_init(void *arg);\n\nconst ShmemCallbacks my_shmem_callbacks = {\n    .request_fn = my_shmem_request,\n    .init_fn = my_shmem_init,\n};\n\n/*\n * Module load callback\n */\nvoid\n_PG_init(void)\n{\n    /*\n     * In order to create our shared memory area, we have to be loaded via\n     * shared_preload_libraries.\n     */\n    if (!process_shared_preload_libraries_in_progress)\n        return;\n\n    /* Register our shared memory needs */\n    RegisterShmemCallbacks(&my_shmem_callbacks);\n}\n\n/* callback to request shmem space */\nstatic void\nmy_shmem_request(void *arg)\n{\n    ShmemRequestStruct(.name = \"My shmem area\",\n                       .size = sizeof(MyShmemData),\n                       .ptr = (void **) &MyShmem,\n        );\n}\n\n/* callback to initialize the contents of the MyShmem area at startup */\nstatic void\nmy_shmem_init(void *arg)\n{\n    int         tranche_id;\n\n    /* Initialize the lock */\n    tranche_id = LWLockNewTrancheId(\"my tranche name\");\n    LWLockInitialize(&MyShmem->lock, tranche_id);\n\n    ... initialize the rest of MyShmem fields ...\n}\n\n
\n

request_fn \u56de\u8c03\u4f1a\u5728\u7cfb\u7edf\u542f\u52a8\u671f\u95f4\u3001\u5171\u4eab\u5185\u5b58\u5c1a\u672a\u5206\u914d\u4e4b\u524d\u88ab\u8c03\u7528\u3002\u5b83\u5e94\u5f53\u8c03\u7528 ShmemRequestStruct() \u6765\u767b\u8bb0\u63d2\u4ef6\u7684\u5171\u4eab\u5185\u5b58\u9700\u6c42\u3002\u6ce8\u610f\uff0cShmemRequestStruct() \u5e76\u4e0d\u4f1a\u7acb\u523b\u5206\u914d\u6216\u521d\u59cb\u5316\u5185\u5b58\uff0c\u5b83\u53ea\u662f\u767b\u8bb0\u7a0d\u540e\u5728\u542f\u52a8\u5e8f\u5217\u4e2d\u8981\u5206\u914d\u7684\u7a7a\u95f4\u3002\u5185\u5b58\u5206\u914d\u5b8c\u6210\u540e\u4f1a\u88ab\u521d\u59cb\u5316\u4e3a\u96f6\u3002\u5bf9\u4e8e\u66f4\u590d\u6742\u7684\u521d\u59cb\u5316\uff0c\u53ef\u8bbe\u7f6e init_fn() \u56de\u8c03\uff1b\u8be5\u56de\u8c03\u4f1a\u5728\u5185\u5b58\u5206\u914d\u5e76\u6e05\u96f6\u4e4b\u540e\u3001\u4f46\u5728\u4efb\u4f55\u5176\u4ed6\u8fdb\u7a0b\u5f00\u59cb\u8fd0\u884c\u4e4b\u524d\u88ab\u8c03\u7528\uff0c\u56e0\u6b64\u4e0d\u9700\u8981\u52a0\u9501\u3002

\n

\u5728 Windows \u4e0a\uff0cattach_fn \u56de\u8c03\u5982\u679c\u5b58\u5728\uff0c\u8fd8\u4f1a\u5728\u6bcf\u6b21\u540e\u7aef\u542f\u52a8\u65f6\u989d\u5916\u88ab\u8c03\u7528\u3002\u5b83\u53ef\u7528\u4e8e\u521d\u59cb\u5316\u4e0e\u5171\u4eab\u5185\u5b58\u533a\u57df\u76f8\u5173\u7684\u5176\u4ed6\u6bcf\u540e\u7aef\u72b6\u6001\uff0c\u800c\u8fd9\u4e9b\u72b6\u6001\u5728\u5176\u4ed6\u7cfb\u7edf\u4e0a\u4f1a\u901a\u8fc7 fork() \u88ab\u7ee7\u627f\u3002

\n

\u5728 PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_stat_statements/pg_stat_statements.c \u91cc\u53ef\u4ee5\u627e\u5230\u4e00\u4e2a\u5206\u914d\u5171\u4eab\u5185\u5b58\u7684\u793a\u4f8b\u3002

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36.10.11.2.\u00a0\u4f7f\u7528 ShmemRequestStruct \u5728\u542f\u52a8\u540e\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

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ShmemRequestStruct() \u4e5f\u53ef\u4ee5\u5728\u7cfb\u7edf\u542f\u52a8\u4e4b\u540e\u8c03\u7528\uff0c\u8fd9\u5bf9\u5141\u8bb8\u5728\u672a\u6307\u5b9a\u4e8eshared_preload_libraries\u4e2d\u7684\u63d2\u4ef6\u5e93\u91cc\u505a\u5c11\u91cf\u5206\u914d\u5f88\u6709\u7528\u3002\u4e0d\u8fc7\uff0c\u5728\u542f\u52a8\u4e4b\u540e\uff0c\u5982\u679c\u53ef\u7528\u5171\u4eab\u5185\u5b58\u4e0d\u8db3\uff0c\u5206\u914d\u53ef\u80fd\u4f1a\u5931\u8d25\u3002\u7cfb\u7edf\u4f1a\u4e3a\u542f\u52a8\u540e\u7684\u5206\u914d\u4fdd\u7559\u4e00\u90e8\u5206\u5185\u5b58\uff0c\u4f46\u8fd9\u4e2a\u4fdd\u7559\u91cf\u5f88\u5c0f\u3002

\n

\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c\u5728\u7cfb\u7edf\u542f\u52a8\u540e\u8c03\u7528 RegisterShmemCallbacks() \u4f1a\u62a5\u9519\u3002\u8981\u5728\u542f\u52a8\u540e\u4f7f\u7528\u5b83\uff0c\u5fc5\u987b\u5728\u4f20\u5165\u7684 ShmemCallbacks \u7ed3\u6784\u4f53\u4e2d\u8bbe\u7f6e SHMEM_CALLBACKS_ALLOW_AFTER_STARTUP \u6807\u5fd7\uff0c\u8868\u793a\u5df2\u77e5\u6653\u98ce\u9669\u3002

\n

\u5f53\u5728\u542f\u52a8\u540e\u8c03\u7528 RegisterShmemCallbacks() \u65f6\uff0c\u5b83\u4f1a\u6839\u636e\u8bf7\u6c42\u7684\u5185\u5b58\u533a\u57df\u662f\u5426\u5df2\u7ecf\u7531\u5176\u4ed6\u540e\u7aef\u521d\u59cb\u5316\u8fc7\uff0c\u7acb\u5373\u8c03\u7528\u76f8\u5e94\u7684\u56de\u8c03\u51fd\u6570\u3002\u56de\u8c03\u51fd\u6570\u4f1a\u5728\u6301\u6709\u5185\u90e8\u9501\uff08ShmemIndexLock\uff09\u7684\u60c5\u51b5\u4e0b\u6267\u884c\uff0c\u8fd9\u53ef\u4ee5\u9632\u6b62\u4e24\u4e2a\u540e\u7aef\u540c\u65f6\u5c1d\u8bd5\u521d\u59cb\u5316\u8be5\u5185\u5b58\u533a\u57df\u65f6\u51fa\u73b0\u7ade\u6001\u6761\u4ef6\u3002\u5982\u679c\u5206\u914d\u6216\u521d\u59cb\u5316\u56e0\u4efb\u4f55\u539f\u56e0\u5931\u8d25\uff0c\u5171\u4eab\u5185\u5b58\u533a\u57df\u4f1a\u5904\u4e8e\u5e9f\u5f03\u72b6\u6001\uff0c\u76f4\u5230\u670d\u52a1\u5668\u91cd\u542f\u524d\uff0c\u4efb\u4f55\u9644\u52a0\u6216\u91cd\u65b0\u521d\u59cb\u5316\u8fd9\u4e9b\u533a\u57df\u7684\u5c1d\u8bd5\u90fd\u4f1a\u5931\u8d25\u3002

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\u540e\u7aef\u9644\u52a0\u5230\u5df2\u5206\u914d\u7684\u5171\u4eab\u5185\u5b58\u533a\u57df\u65f6\uff0c\u901a\u5e38\u5fc5\u987b\u5411 ShmemRequestStruct() \u4f20\u5165\u5206\u914d\u8be5\u533a\u57df\u65f6\u4f7f\u7528\u7684\u76f8\u540c\u5927\u5c0f\uff1b\u5927\u5c0f\u4e0d\u5339\u914d\u4f1a\u62a5\u9519\u3002\u5982\u679c\u9644\u52a0\u7684\u540e\u7aef\u4e8b\u5148\u4e0d\u77e5\u9053\u5927\u5c0f\uff0c\u53ef\u4ee5\u6539\u4e3a\u4f20\u5165 SHMEM_ATTACH_UNKNOWN_SIZE\uff0c\u8df3\u8fc7\u6b64\u4ea4\u53c9\u68c0\u67e5\u3002SHMEM_ATTACH_UNKNOWN_SIZE \u53ea\u80fd\u7528\u4e8e\u9644\u52a0\u5230\u5df2\u5b58\u5728\u7684\u533a\u57df\uff1b\u5728\u5206\u914d\u533a\u57df\u4e4b\u524d\u4f7f\u7528\u5b83\u4f1a\u62a5\u9519\u3002

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36.10.11.3.\u00a0\u542f\u52a8\u540e\u5206\u914d\u52a8\u6001\u5171\u4eab\u5185\u5b58

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\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u4e4b\u540e\u5b8c\u6210\u3002\u4e3a\u6b64\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8be5\u5171\u4eab\u5185\u5b58\u7684\u540e\u7aef\u90fd\u5e94\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u83b7\u53d6\u4e00\u4e2a\u6307\u9488\uff1a

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void *GetNamedDSMSegment(const char *name, size_t size,\n                         void (*init_callback) (void *ptr, void *arg),\n                         bool *found, void *arg)\n
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\u5982\u679c\u7ed9\u5b9a\u540d\u79f0\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u5c1a\u4e0d\u5b58\u5728\uff0c\u8be5\u51fd\u6570\u4f1a\u5206\u914d\u8be5\u6bb5\uff0c\u5e76\u4f7f\u7528\u63d0\u4f9b\u7684 init_callback \u56de\u8c03\u51fd\u6570\u5bf9\u5176\u8fdb\u884c\u521d\u59cb\u5316\u3002\u5982\u679c\u8be5\u6bb5\u5df2\u7ecf\u7531\u53e6\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8fc7\uff0c\u8be5\u51fd\u6570\u5c31\u53ea\u4f1a\u628a\u73b0\u6709\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u9644\u52a0\u5230\u5f53\u524d\u540e\u7aef\u3002\u5728\u524d\u4e00\u79cd\u60c5\u51b5\u4e0b\uff0cGetNamedDSMSegment \u4f1a\u628a void *arg \u53c2\u6570\u4f20\u7ed9 init_callback\u3002\u8fd9\u5bf9\u5728\u591a\u4e2a DSM \u6bb5\u4e4b\u95f4\u590d\u7528\u521d\u59cb\u5316\u56de\u8c03\u51fd\u6570\u7279\u522b\u6709\u7528\u3002

\n

GetNamedDSMSegment \u4f1a\u786e\u4fdd\u53ea\u6709\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8be5\u5185\u5b58\u6bb5\uff0c\u800c\u5176\u4ed6\u6240\u6709\u540e\u7aef\u90fd\u4f1a\u83b7\u5f97\u6307\u5411\u540c\u4e00\u5757\u5df2\u5b8c\u5168\u5206\u914d\u5e76\u521d\u59cb\u5316\u597d\u7684\u5185\u5b58\u6bb5\u7684\u6307\u9488\u3002

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GetNamedDSMSegment \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/test_dsm_registry/test_dsm_registry.c\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

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36.10.12. \u8f7b\u91cf\u7ea7\u9501\uff08LWLocks\uff09

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36.10.12.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42 LWLocks

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\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLocks\u3002\u4e0e\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u4e00\u6837\uff0c\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\uff0c\u5e76\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\u3002\u6b64\u94a9\u5b50\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8fd9\u786e\u4fdd\u5b58\u5728\u4e00\u4e2a\u540d\u4e3a tranche_name\u3001\u5305\u542b num_lwlocks \u4e2a LWLocks \u7684\u6570\u7ec4\u3002\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u53d6\u5f97\u8be5\u6570\u7ec4\u7684\u6307\u9488\uff1a

\n
LWLockPadded *GetNamedLWLockTranche(const char *tranche_name)\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.12.2.\u00a0\u542f\u52a8\u540e\u8bf7\u6c42 LWLocks

\n
\n
\n

\n
\n
\n
\n

\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u83b7\u53d6 LWLocks \u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u540e\u8fdb\u884c\uff0c\u4e5f\u65e0\u9700\u501f\u52a9 shmem_request_hook\u3002\u4e3a\u6b64\uff0c\u9996\u5148\u901a\u8fc7\u8c03\u7528\u4e0b\u9762\u7684\u51fd\u6570\u5206\u914d\u4e00\u4e2a tranche_id\uff1a

\n
int LWLockNewTrancheId(const char *name)\n
\n

\u63a5\u4e0b\u6765\uff0c\u521d\u59cb\u5316\u6bcf\u4e2a LWLock\uff0c\u5e76\u628a\u65b0\u7684 tranche_id \u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\uff1a

\n
void LWLockInitialize(LWLock *lock, int tranche_id)\n
\n

\u4e0e\u5171\u4eab\u5185\u5b58\u7c7b\u4f3c\uff0c\u6bcf\u4e2a\u540e\u7aef\u90fd\u5e94\u786e\u4fdd\u53ea\u6709\u4e00\u4e2a\u8fdb\u7a0b\u4f1a\u5206\u914d\u65b0\u7684 tranche_id \u5e76\u521d\u59cb\u5316\u6bcf\u4e00\u4e2a\u65b0\u7684 LWLock\u3002\u4e00\u79cd\u505a\u6cd5\u662f\u4ec5\u5728\u6301\u6709 AddinShmemInitLock \u72ec\u5360\u9501\u7684\u5171\u4eab\u5185\u5b58\u521d\u59cb\u5316\u4ee3\u7801\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u3002\u5982\u679c\u4f7f\u7528 GetNamedDSMSegment\uff0c\u90a3\u4e48\u5728 init_callback \u56de\u8c03\u51fd\u6570\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u5c31\u8db3\u4ee5\u907f\u514d\u7ade\u4e89\u6761\u4ef6\u3002

\n

LWLockNewTrancheId \u548c LWLockInitialize \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_prewarm/autoprewarm.c\u3002

\n
\n
\n
\n
\n
\n
\n

36.10.13. \u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6

\n
\n
\n
\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u5728\u7b49\u5f85\u4e8b\u4ef6\u7c7b\u578b Extension \u4e0b\u5b9a\u4e49\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\uff1a

\n
uint32 WaitEventExtensionNew(const char *wait_event_name)\n
\n

\u8be5\u7b49\u5f85\u4e8b\u4ef6\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u9762\u5411\u7528\u6237\u7684\u81ea\u5b9a\u4e49\u5b57\u7b26\u4e32\u3002\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/worker_spi\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n

\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\u53ef\u4ee5\u5728 pg_stat_activity \u4e2d\u67e5\u770b\uff1a

\n
=# SELECT wait_event_type, wait_event FROM pg_stat_activity\n     WHERE backend_type ~ 'worker_spi';\n wait_event_type |  wait_event\n-----------------+---------------\n Extension       | WorkerSpiMain\n(1 row)\n
\n
\n
\n
\n
\n
\n

36.10.14. \u6ce8\u5165\u70b9

\n
\n
\n
\n

\u7ed9\u5b9a\u540d\u79f0 name \u7684\u6ce8\u5165\u70b9\u53ef\u901a\u8fc7\u4ee5\u4e0b\u5b8f\u58f0\u660e\uff1a

\n
INJECTION_POINT(name, arg);\n
\n

\u670d\u52a1\u5668\u4ee3\u7801\u4e2d\u5df2\u7ecf\u5728\u82e5\u5e72\u5173\u952e\u4f4d\u7f6e\u58f0\u660e\u4e86\u6ce8\u5165\u70b9\u3002\u65b0\u589e\u6ce8\u5165\u70b9\u540e\uff0c\u9700\u8981\u91cd\u65b0\u7f16\u8bd1\u4ee3\u7801\uff0c\u624d\u80fd\u8ba9\u8be5\u6ce8\u5165\u70b9\u51fa\u73b0\u5728\u4e8c\u8fdb\u5236\u6587\u4ef6\u4e2d\u3002\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u4e5f\u53ef\u4ee5\u4f7f\u7528\u540c\u4e00\u4e2a\u5b8f\u5728\u81ea\u5df1\u7684\u4ee3\u7801\u4e2d\u58f0\u660e\u6ce8\u5165\u70b9\u3002\u6ce8\u5165\u70b9\u540d\u79f0\u5e94\u4f7f\u7528\u5c0f\u5199\u5b57\u6bcd\uff0c\u5e76\u7528\u8fde\u5b57\u7b26\u5206\u9694\u5404\u4e2a\u672f\u8bed\u3002arg \u662f\u8fd0\u884c\u65f6\u4f20\u7ed9\u56de\u8c03\u7684\u53ef\u9009\u53c2\u6570\u503c\u3002

\n

\u6267\u884c\u6ce8\u5165\u70b9\u53ef\u80fd\u9700\u8981\u5206\u914d\u5c11\u91cf\u5185\u5b58\uff0c\u800c\u8fd9\u53ef\u80fd\u5931\u8d25\u3002\u5982\u679c\u4f60\u9700\u8981\u5728\u4e00\u4e2a\u4e0d\u5141\u8bb8\u52a8\u6001\u5206\u914d\u7684\u4e34\u754c\u533a\u4e2d\u4f7f\u7528\u6ce8\u5165\u70b9\uff0c\u53ef\u4ee5\u91c7\u7528\u4ee5\u4e0b\u4e24\u6b65\u6cd5\uff1a

\n
INJECTION_POINT_LOAD(name);\nINJECTION_POINT_CACHED(name, arg);\n
\n

\u5728\u8fdb\u5165\u4e34\u754c\u533a\u4e4b\u524d\uff0c\u8c03\u7528 INJECTION_POINT_LOAD\u3002\u5b83\u4f1a\u68c0\u67e5\u5171\u4eab\u5185\u5b58\u72b6\u6001\uff0c\u5e76\u5728\u8be5\u6ce8\u5165\u70b9\u5904\u4e8e\u6fc0\u6d3b\u72b6\u6001\u65f6\u628a\u56de\u8c03\u52a0\u8f7d\u5230\u540e\u7aef\u79c1\u6709\u5185\u5b58\u4e2d\u3002\u5728\u4e34\u754c\u533a\u5185\u90e8\uff0c\u518d\u7528 INJECTION_POINT_CACHED \u6765\u6267\u884c\u56de\u8c03\u3002

\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u4e3a\u4e00\u4e2a\u5df2\u7ecf\u58f0\u660e\u597d\u7684\u6ce8\u5165\u70b9\u9644\u52a0\u56de\u8c03\uff1a

\n
extern void InjectionPointAttach(const char *name,\n                                 const char *library,\n                                 const char *function,\n                                 const void *private_data,\n                                 int private_data_size);\n
\n

name \u662f\u6ce8\u5165\u70b9\u7684\u540d\u79f0\uff1b\u6267\u884c\u5230\u8fbe\u6b64\u6ce8\u5165\u70b9\u65f6\uff0c\u5c06\u6267\u884c\u4ece library \u52a0\u8f7d\u7684\u51fd\u6570\u3002private_data \u662f\u4e00\u5757\u5927\u5c0f\u4e3a private_data_size \u7684\u79c1\u6709\u6570\u636e\u533a\u57df\uff0c\u5728\u6267\u884c\u56de\u8c03\u65f6\u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\u3002

\n

\u4e0b\u9762\u662f\u4e00\u4e2a InjectionPointCallback \u7684\u793a\u4f8b\uff1a

\n
static void\ncustom_injection_callback(const char *name,\n                          const void *private_data,\n                          void *arg)\n{\n    uint32 wait_event_info = WaitEventInjectionPointNew(name);\n\n    pgstat_report_wait_start(wait_event_info);\n    elog(NOTICE, \"%s: executed custom callback\", name);\n    pgstat_report_wait_end();\n}\n
\n

\u8fd9\u4e2a\u56de\u8c03\u4f1a\u4ee5 NOTICE \u7ea7\u522b\u5411\u670d\u52a1\u5668\u9519\u8bef\u65e5\u5fd7\u5199\u5165\u4e00\u6761\u6d88\u606f\uff0c\u4f46\u56de\u8c03\u5b8c\u5168\u53ef\u4ee5\u5b9e\u73b0\u66f4\u590d\u6742\u7684\u903b\u8f91\u3002

\n

\u53e6\u4e00\u79cd\u5b9a\u4e49\u201c\u5230\u8fbe\u6ce8\u5165\u70b9\u65f6\u5e94\u6267\u884c\u4ec0\u4e48\u52a8\u4f5c\u201d\u7684\u65b9\u5f0f\uff0c\u662f\u628a\u6d4b\u8bd5\u4ee3\u7801\u76f4\u63a5\u5199\u5728\u5e38\u89c4\u6e90\u4ee3\u7801\u65c1\u8fb9\u3002\u5982\u679c\u8be5\u52a8\u4f5c\u4f9d\u8d56\u4e8e\u52a0\u8f7d\u6a21\u5757\u65e0\u6cd5\u8bbf\u95ee\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u8fd9\u4f1a\u5f88\u6709\u7528\u3002\u6b64\u65f6\u53ef\u4ee5\u4f7f\u7528 IS_INJECTION_POINT_ATTACHED \u5b8f\u6765\u68c0\u67e5\u67d0\u4e2a\u6ce8\u5165\u70b9\u662f\u5426\u5df2\u9644\u52a0\uff0c\u4f8b\u5982\uff1a

\n
#ifdef USE_INJECTION_POINTS\nif (IS_INJECTION_POINT_ATTACHED(\"before-foobar\"))\n{\n    /* change a local variable if injection point is attached */\n    local_var = 123;\n\n    /* also execute the callback */\n    INJECTION_POINT_CACHED(\"before-foobar\", NULL);\n}\n#endif\n
\n

\u6ce8\u610f\uff0c\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u4e0a\u7684\u56de\u8c03\u4e0d\u4f1a\u7531 IS_INJECTION_POINT_ATTACHED \u5b8f\u6267\u884c\u3002\u5982\u679c\u4f60\u60f3\u6267\u884c\u8be5\u56de\u8c03\uff0c\u5c31\u5fc5\u987b\u50cf\u4e0a\u9762\u7684\u793a\u4f8b\u90a3\u6837\u53e6\u5916\u8c03\u7528 INJECTION_POINT_CACHED\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e5f\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u89e3\u9664\u4e00\u4e2a\u6ce8\u5165\u70b9\uff1a

\n
extern bool InjectionPointDetach(const char *name);\n
\n

\u6210\u529f\u65f6\u8fd4\u56de true\uff0c\u5426\u5219\u8fd4\u56de false\u3002

\n

\u4e00\u4e2a\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u7684\u56de\u8c03\u4f1a\u5728\u6240\u6709\u540e\u7aef\u4e2d\u751f\u6548\uff0c\u5305\u62ec\u5728\u8c03\u7528 InjectionPointAttach \u4e4b\u540e\u624d\u542f\u52a8\u7684\u540e\u7aef\u3002\u5b83\u4f1a\u4e00\u76f4\u4fdd\u6301\u9644\u52a0\u72b6\u6001\uff0c\u76f4\u5230\u670d\u52a1\u5668\u505c\u6b62\uff0c\u6216\u8005\u901a\u8fc7 InjectionPointDetach \u5c06\u5176\u89e3\u9664\u3002

\n

\u76f8\u5173\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 src/test/modules/injection_points\u3002

\n

\u8981\u542f\u7528\u6ce8\u5165\u70b9\uff0c\u4f7f\u7528 configure \u65f6\u9700\u6307\u5b9a --enable-injection-points\uff0c\u4f7f\u7528 Meson \u65f6\u9700\u6307\u5b9a -Dinjection_points=true\u3002

\n
\n
\n
\n
\n
\n

36.10.15. \u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1

\n
\n
\n
\n

\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u53ef\u4ee5\u4f7f\u7528\u5728\u7d2f\u8ba1\u7edf\u8ba1\u7cfb\u7edf\u4e2d\u6ce8\u518c\u7684\u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1\u7c7b\u578b\u3002

\n

\u9996\u5148\uff0c\u5b9a\u4e49\u4e00\u4e2a PgStat_KindInfo\uff0c\u5176\u4e2d\u5305\u542b\u4e0e\u6240\u6ce8\u518c\u81ea\u5b9a\u4e49\u7c7b\u578b\u76f8\u5173\u7684\u5168\u90e8\u4fe1\u606f\u3002\u4f8b\u5982\uff1a

\n
static const PgStat_KindInfo custom_stats = {\n    .name = \"custom_stats\",\n    .fixed_amount = false,\n    .shared_size = sizeof(PgStatShared_Custom),\n    .shared_data_off = offsetof(PgStatShared_Custom, stats),\n    .shared_data_len = sizeof(((PgStatShared_Custom *) 0)->stats),\n    .pending_size = sizeof(PgStat_StatCustomEntry),\n}\n
\n

\u7136\u540e\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8fd9\u79cd\u81ea\u5b9a\u4e49\u7c7b\u578b\u7684\u540e\u7aef\uff0c\u90fd\u9700\u8981\u4f7f\u7528 pgstat_register_kind \u6ce8\u518c\u5b83\uff0c\u5e76\u6307\u5b9a\u4e00\u4e2a\u7528\u4e8e\u5b58\u50a8\u8be5\u7c7b\u7edf\u8ba1\u6761\u76ee\u7684\u552f\u4e00 ID\uff1a

\n
extern PgStat_Kind pgstat_register_kind(PgStat_Kind kind,\n                                        const PgStat_KindInfo *kind_info);\n
\n

\u5728\u5f00\u53d1\u65b0\u6269\u5c55\u65f6\uff0c\u5e94\u5c06 PGSTAT_KIND_EXPERIMENTAL \u7528\u4f5c kind\u3002\u5f53\u4f60\u51c6\u5907\u628a\u6269\u5c55\u53d1\u5e03\u7ed9\u7528\u6237\u65f6\uff0c\u8bf7\u5728 Custom Cumulative Statistics \u9875\u9762\u4e0a\u9884\u7559\u4e00\u4e2a kind ID\u3002

\n

\u5173\u4e8e PgStat_KindInfo API \u7684\u7ec6\u8282\uff0c\u53ef\u89c1 src/include/utils/pgstat_internal.h\u3002

\n

\u5df2\u6ce8\u518c\u7684\u7edf\u8ba1\u7c7b\u578b\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u540d\u79f0\u4ee5\u53ca\u4e00\u4e2a\u5728\u5171\u4eab\u5185\u5b58\u4e2d\u4f9b\u6574\u4e2a\u670d\u52a1\u5668\u5171\u4eab\u7684\u552f\u4e00 ID\u3002\u6bcf\u4e2a\u4f7f\u7528\u81ea\u5b9a\u4e49\u7edf\u8ba1\u7c7b\u578b\u7684\u540e\u7aef\u90fd\u4f1a\u7ef4\u62a4\u4e00\u4e2a\u672c\u5730\u7f13\u5b58\uff0c\u7528\u6765\u4fdd\u5b58\u5404\u4e2a\u81ea\u5b9a\u4e49 PgStat_KindInfo \u7684\u4fe1\u606f\u3002

\n

\u5e94\u5c06\u5b9e\u73b0\u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1\u7c7b\u578b\u7684\u6269\u5c55\u6a21\u5757\u52a0\u5165shared_preload_libraries\uff0c\u4ee5\u4fbf\u5728 PostgreSQL \u542f\u52a8\u671f\u95f4\u5c3d\u65e9\u8f7d\u5165\u3002

\n

\u5c55\u793a\u5982\u4f55\u6ce8\u518c\u5e76\u4f7f\u7528\u81ea\u5b9a\u4e49\u7edf\u8ba1\u4fe1\u606f\u7684\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/test_custom_stats\u3002

\n
\n
\n
\n
\n
\n

36.10.16. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern \"C\" \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern \"C\"\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

    \n
    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u9694\u79bb\u5728\u4e00\u5c42\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern \"C\"\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

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"#XFUNC-C/div[18]/p[15]", "#XFUNC-C/div[18]/p[16]", "#XFUNC-C/div[18]/p[18]", "#XFUNC-C/div[18]/p[19]", "#XFUNC-C/div[18]/p[1]", "#XFUNC-C/div[18]/p[20]", "#XFUNC-C/div[18]/p[3]", "#XFUNC-C/div[18]/p[4]", "#XFUNC-C/div[18]/p[6]", "#XFUNC-C/div[18]/p[7]", "#XFUNC-C/div[19]/p[10]", "#XFUNC-C/div[19]/p[1]", "#XFUNC-C/div[19]/p[2]", "#XFUNC-C/div[19]/p[4]", "#XFUNC-C/div[19]/p[6]", "#XFUNC-C/div[19]/p[7]", "#XFUNC-C/div[19]/p[8]", "#XFUNC-C/div[19]/p[9]", "#XFUNC-C/div[1]/dl[0]/dt[0]", "#XFUNC-C/div[1]/dl[0]/dt[10]", "#XFUNC-C/div[1]/dl[0]/dt[12]", "#XFUNC-C/div[1]/dl[0]/dt[13]", "#XFUNC-C/div[1]/dl[0]/dt[14]", "#XFUNC-C/div[1]/dl[0]/dt[15]", "#XFUNC-C/div[1]/dl[0]/dt[1]", "#XFUNC-C/div[1]/dl[0]/dt[2]", "#XFUNC-C/div[1]/dl[0]/dt[3]", "#XFUNC-C/div[1]/dl[0]/dt[4]", "#XFUNC-C/div[1]/dl[0]/dt[5]", "#XFUNC-C/div[1]/dl[0]/dt[6]", "#XFUNC-C/div[1]/dl[0]/dt[7]", "#XFUNC-C/div[1]/dl[0]/dt[8]", "#XFUNC-C/div[1]/dl[0]/dt[9]", "#XFUNC-C/div[20]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[20]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[20]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[20]/p[2]", "#XFUNC-C/div[20]/p[4]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[0]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[1]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[2]", "#XFUNC-C/div[5]/div[4]/ol[0]/li[3]", "#XFUNC-C/div[5]/div[9]/h3[0]", "#XFUNC-C/div[5]/div[9]/p[1]", "#XFUNC-C/div[5]/p[12]", "#XFUNC-C/div[5]/p[14]", "#XFUNC-C/div[5]/p[16]", "#XFUNC-C/div[5]/p[18]", "#XFUNC-C/div[5]/p[19]", "#XFUNC-C/div[5]/p[22]", "#XFUNC-C/div[5]/p[2]", "#XFUNC-C/div[5]/p[3]", "#XFUNC-C/div[5]/p[5]", "#XFUNC-C/div[5]/p[6]", "#XFUNC-C/div[5]/p[7]", "#XFUNC-C/div[5]/p[8]", "#XFUNC-C/div[6]/div[13]/h3[0]", "#XFUNC-C/div[6]/div[13]/p[1]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[0]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/tbody[2]/tr[3]/td[2]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[0]", "#XFUNC-C/div[6]/div[21]/div[1]/table[0]/thead[1]/tr[0]/th[1]", "#XFUNC-C/div[6]/div[21]/p[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[0]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[1]", "#XFUNC-C/div[6]/div[4]/ul[0]/li[2]", "#XFUNC-C/div[6]/p[10]", "#XFUNC-C/div[6]/p[11]", "#XFUNC-C/div[6]/p[12]", "#XFUNC-C/div[6]/p[14]", "#XFUNC-C/div[6]/p[16]", "#XFUNC-C/div[6]/p[17]", "#XFUNC-C/div[6]/p[19]", "#XFUNC-C/div[6]/p[20]", "#XFUNC-C/div[6]/p[20]/span[2]/span[0]", "#XFUNC-C/div[6]/p[23]", "#XFUNC-C/div[6]/p[2]", "#XFUNC-C/div[6]/p[3]", "#XFUNC-C/div[6]/p[5]", "#XFUNC-C/div[6]/p[7]", "#XFUNC-C/div[6]/p[8]", "#XFUNC-C/div[7]/p[10]", "#XFUNC-C/div[7]/p[13]", "#XFUNC-C/div[7]/p[16]", "#XFUNC-C/div[7]/p[17]", "#XFUNC-C/div[7]/p[18]", "#XFUNC-C/div[7]/p[1]", "#XFUNC-C/div[7]/p[20]", "#XFUNC-C/div[7]/p[3]", "#XFUNC-C/div[7]/p[5]", "#XFUNC-C/div[7]/p[6]", "#XFUNC-C/div[7]/p[7]", "#XFUNC-C/div[7]/p[8]", "#XFUNC-C/div[7]/p[9]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[0]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[1]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[2]", "#XFUNC-C/div[8]/div[3]/ul[0]/li[3]", 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"description": ["\u52a8\u6001\u52a0\u8f7d\u7684 C \u51fd\u6570"], "manual_html": "
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36.10.\u00a0C \u8bed\u8a00\u51fd\u6570

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\u7528\u6237\u5b9a\u4e49\u7684\u51fd\u6570\u53ef\u4ee5\u7528 C \u7f16\u5199\uff08\u6216\u8005\u53ef\u4ee5\u4e0e C \u517c\u5bb9\u7684\u8bed\u8a00\uff0c\u4f8b\u5982 C++\uff09\u3002\u8fd9\u7c7b\u51fd\u6570\u88ab\u7f16\u8bd1\u6210\u52a8\u6001\u8f7d\u5165\u5bf9\u8c61\uff08\u4e5f\u88ab\u79f0\u4e3a\u5171\u4eab\u5e93\uff09\u5e76\u4e14\u7531\u670d\u52a1\u5668\u5728\u9700\u8981\u65f6\u8f7d\u5165\u3002\u52a8\u6001\u8f7d\u5165\u662f\u628a\u201cC\u8bed\u8a00\u201d\u51fd\u6570\u548c\u201c\u5185\u90e8\u201d\u51fd\u6570\u533a\u5206\u5f00\u7684\u7279\u6027 \u2014 \u4e24\u8005\u771f\u6b63\u7684\u7f16\u7801\u4e60\u60ef\u5b9e\u9645\u4e0a\u662f\u4e00\u6837\u7684\uff08\u56e0\u6b64\uff0c\u6807\u51c6\u5185\u90e8\u51fd\u6570\u5e93\u4e3a\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u7f16\u7801\u793a\u4f8b\uff09\u3002

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\u76ee\u524d C \u51fd\u6570\u4ec5\u4f7f\u7528\u4e00\u79cd\u8c03\u7528\u7ea6\u5b9a\uff08\u201c\u7248\u672c 1\u201d\uff09\u3002\u901a\u8fc7\u4e3a\u51fd\u6570\u7f16\u5199 PG_FUNCTION_INFO_V1() \u5b8f\u8c03\u7528\u6765\u8868\u660e\u652f\u6301\u6b64\u8c03\u7528\u7ea6\u5b9a\uff0c\u793a\u4f8b\u5982\u4e0b\u3002

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36.10.1. \u52a8\u6001\u8f7d\u5165

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\u5728\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u7b2c\u4e00\u6b21\u8c03\u7528\u4e00\u4e2a\u7279\u5b9a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4e2d\u7684\u7528\u6237\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u4f1a\u628a\u90a3\u4e2a\u76ee\u6807\u6587\u4ef6\u8f7d\u5165\u5230\u5185\u5b58\u4ee5\u4fbf\u8be5\u51fd\u6570\u88ab\u8c03\u7528\u3002\u56e0\u6b64\u7528\u6237\u5b9a\u4e49\u7684 C \u51fd\u6570\u7684CREATE FUNCTION\u5fc5\u987b\u4e3a\u8be5\u51fd\u6570\u6307\u5b9a\u4e24\u5757\u4fe1\u606f\uff1a\u53ef\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u8981\u5728\u8be5\u76ee\u6807\u6587\u4ef6\u4e2d\u8c03\u7528\u7684\u7279\u5b9a\u51fd\u6570\u7684 C \u540d\u79f0\uff08\u94fe\u63a5\u7b26\u53f7\uff09\u3002\u5982\u679c\u6ca1\u6709\u663e\u5f0f\u6307\u5b9a C \u540d\u79f0\uff0c\u5219\u5b83\u88ab\u5047\u5b9a\u4e3a\u548c SQL \u51fd\u6570\u540d\u76f8\u540c\u3002

\n

\u4e0b\u9762\u7684\u7b97\u6cd5\u88ab\u7528\u6765\u57fa\u4e8eCREATE FUNCTION \u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u540d\u79f0\u6765\u5b9a\u4f4d\u5171\u4eab\u76ee\u6807\u6587\u4ef6\uff1a

\n
\n
    \n
  1. \n

    \u5982\u679c\u540d\u79f0\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u5219\u8f7d\u5165\u7ed9\u5b9a\u7684\u6587\u4ef6\u3002

    \n
    2. \n
  2. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4ee5\u5b57\u7b26\u4e32$libdir\u5f00\u59cb\uff0c\u90a3\u4e48\u8fd9\u4e00\u90e8\u5206\u4f1a\u88ab PostgreSQL\u5305\u7684\u5e93\u76ee\u5f55\u540d\uff08\u5728\u7f16\u8bd1\u65f6\u786e\u5b9a\uff09\u66ff\u6362\u3002

    \n
    3. \n
  3. \n

    \u5982\u679c\u8be5\u540d\u79f0\u4e0d\u5305\u542b\u76ee\u5f55\u90e8\u5206\uff0c\u4f1a\u5728\u914d\u7f6e\u53d8\u91cfdynamic_library_path\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u641c\u7d22\u8be5\u6587\u4ef6\u3002

    \n
    4. \n
  4. \n

    \u5426\u5219\uff08\u5728\u8be5\u8def\u5f84\u4e2d\u6ca1\u627e\u5230\u8be5\u6587\u4ef6\uff0c\u6216\u8005\u5b83\u5305\u542b\u4e00\u4e2a\u975e\u7edd\u5bf9\u76ee\u5f55\uff09\uff0c\u52a8\u6001\u8f7d\u5165\u5668\u5c06\u5c1d\u8bd5\u63a5\u53d7\u7ed9\u5b9a\u7684\u540d\u79f0\uff0c\u8fd9\u5f88\u53ef\u80fd\u4f1a\u5931\u8d25\uff08\u4f9d\u8d56\u5f53\u524d\u5de5\u4f5c\u76ee\u5f55\u662f\u4e0d\u53ef\u9760\u7684\uff09\u3002

    \n
    5. \n
\n
\n

\u5982\u679c\u8fd9\u4e2a\u5e8f\u5217\u4e0d\u8d77\u4f5c\u7528\uff0c\u4f1a\u628a\u5e73\u53f0\u76f8\u5173\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u540d\u6269\u5c55\uff08\u901a\u5e38\u662f .so\uff09\u8ffd\u52a0\u5230\u7ed9\u5b9a\u7684\u540d\u79f0\u5e76\u4e14\u518d\u6b21\u5c1d\u8bd5\u4e0a\u8ff0\u7684\u8fc7\u7a0b\u3002\u5982\u679c\u8fd8\u662f\u5931\u8d25\uff0c\u5219\u8f7d\u5165\u5931\u8d25\u3002

\n

\u5efa\u8bae\u901a\u8fc7\u76f8\u5bf9\u4e8e $libdir \u7684\u8def\u5f84\uff0c\u6216\u8005\u901a\u8fc7\u52a8\u6001\u5e93\u8def\u5f84\u6765\u5b9a\u4f4d\u5171\u4eab\u5e93\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u5982\u679c\u65b0\u5b89\u88c5\u4f4d\u4e8e\u4e0d\u540c\u7684\u4f4d\u7f6e\uff0c\u7248\u672c\u5347\u7ea7\u4f1a\u66f4\u7b80\u5355\u3002$libdir \u5b9e\u9645\u4ee3\u8868\u7684\u76ee\u5f55\u53ef\u4ee5\u901a\u8fc7\u547d\u4ee4 pg_config --pkglibdir \u67e5\u51fa\u3002

\n

\u7528\u4e8e\u8fd0\u884cPostgreSQL\u670d\u52a1\u5668\u7684\u7528\u6237 ID \u5fc5\u987b\u80fd\u591f\u904d\u5386\u901a\u5f80\u8981\u8f7d\u5165\u6587\u4ef6\u7684\u8def\u5f84\u3002\u5e38\u89c1\u7684\u9519\u8bef\u662f\u628a\u6587\u4ef6\u6216\u66f4\u9ad8\u5c42\u7684\u76ee\u5f55\u53d8\u5f97\u5bf9postgres\u7528\u6237\u4e0d\u53ef\u8bfb\u6216\u8005\u4e0d\u53ef\u6267\u884c\u3002

\n

\u5728\u4efb\u4f55\u60c5\u51b5\u4e0b\uff0cCREATE FUNCTION\u547d\u4ee4\u4e2d\u7ed9\u5b9a\u7684\u6587\u4ef6\u540d\u4f1a\u88ab\u539f\u5c01\u4e0d\u52a8\u5730\u8bb0\u5f55\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\uff0c\u8fd9\u6837\u5982\u679c\u9700\u8981\u518d\u6b21\u8f7d\u5165\u8be5\u6587\u4ef6\u5219\u4f1a\u5e94\u7528\u540c\u6837\u7684\u8fc7\u7a0b\u3002

\n
\n

\u6ce8\u610f

\n

PostgreSQL\u4e0d\u4f1a\u81ea\u52a8\u7f16\u8bd1 C \u51fd\u6570\u3002\u5728\u4eceCREATE FUNCTION\u547d\u4ee4\u4e2d\u5f15\u7528\u76ee\u6807\u6587\u4ef6\u4e4b\u524d\uff0c\u5b83\u5fc5\u987b\u5148\u88ab\u7f16\u8bd1\u597d\u3002\u66f4\u591a\u4fe1\u606f\u8bf7\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

\n
\n

\u4e3a\u786e\u4fdd\u52a8\u6001\u88c5\u8f7d\u7684\u76ee\u6807\u6587\u4ef6\u4e0d\u4f1a\u88ab\u52a0\u8f7d\u5230\u4e0d\u517c\u5bb9\u7684\u670d\u52a1\u5668\u4e2d\uff0cPostgreSQL \u4f1a\u68c0\u67e5\u8be5\u6587\u4ef6\u662f\u5426\u5305\u542b\u5185\u5bb9\u6b63\u786e\u7684\u201c\u9b54\u6570\u5757\u201d\u3002\u8fd9\u6837\u670d\u52a1\u5668\u5c31\u80fd\u68c0\u6d4b\u51fa\u660e\u663e\u7684\u4e0d\u517c\u5bb9\u60c5\u51b5\uff0c\u4f8b\u5982\u4ee3\u7801\u662f\u9488\u5bf9\u53e6\u4e00\u4e2a PostgreSQL \u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u3002\u8981\u52a0\u5165\u9b54\u6570\u5757\uff0c\u8bf7\u5728\u6a21\u5757\u67d0\u4e00\u4e2a\uff08\u4e14\u53ea\u80fd\u4e00\u4e2a\uff09\u6e90\u6587\u4ef6\u4e2d\uff0c\u5728\u5305\u542b\u5934\u6587\u4ef6 fmgr.h \u4e4b\u540e\u5199\u5165\uff1a

\n
PG_MODULE_MAGIC;\n
\n

\u6216\u8005

\n
PG_MODULE_MAGIC_EXT(parameters);\n
\n

PG_MODULE_MAGIC_EXT \u8fd9\u79cd\u5f62\u5f0f\u5141\u8bb8\u4e3a\u6a21\u5757\u6307\u5b9a\u9644\u52a0\u4fe1\u606f\uff1b\u76ee\u524d\u53ef\u4ee5\u6dfb\u52a0\u540d\u79f0\u548c/\u6216\u7248\u672c\u5b57\u7b26\u4e32\u3002\uff08\u5c06\u6765\u53ef\u80fd\u5141\u8bb8\u66f4\u591a\u5b57\u6bb5\u3002\uff09\u53ef\u4ee5\u5199\u6210\u8fd9\u6837\uff1a

\n
PG_MODULE_MAGIC_EXT(\n    .name = \"my_module_name\",\n    .version = \"1.2.3\"\n);\n
\n

\u4e4b\u540e\uff0c\u540d\u79f0\u548c\u7248\u672c\u53ef\u4ee5\u901a\u8fc7 pg_get_loaded_modules() \u51fd\u6570\u67e5\u770b\u3002\u7248\u672c\u5b57\u7b26\u4e32\u7684\u5177\u4f53\u542b\u4e49\u4e0d\u53d7 PostgreSQL \u9650\u5236\uff0c\u4f46\u5efa\u8bae\u91c7\u7528\u8bed\u4e49\u5316\u7248\u672c\u89c4\u5219\u3002

\n

\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u4e4b\u540e\uff0c\u52a8\u6001\u8f7d\u5165\u76ee\u6807\u6587\u4ef6\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002\u5728\u540c\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\uff0c\u540e\u7eed\u5bf9\u8be5\u6587\u4ef6\u4e2d\u51fd\u6570\u7684\u8c03\u7528\u53ea\u9700\u4ed8\u51fa\u4e00\u6b21\u5f88\u5c0f\u7684\u7b26\u53f7\u8868\u67e5\u627e\u5f00\u9500\u3002\u5982\u679c\u9700\u8981\u5f3a\u5236\u91cd\u65b0\u8f7d\u5165\u4e00\u4e2a\u76ee\u6807\u6587\u4ef6\uff08\u4f8b\u5982\u5728\u91cd\u65b0\u7f16\u8bd1\u4e4b\u540e\uff09\uff0c\u5c31\u9700\u8981\u5f00\u542f\u4e00\u4e2a\u65b0\u7684\u4f1a\u8bdd\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u53ef\u4ee5\u5305\u542b\u4e00\u4e2a\u521d\u59cb\u5316\u51fd\u6570\u3002\u5982\u679c\u6587\u4ef6\u5305\u542b\u4e00\u4e2a\u540d\u4e3a _PG_init\u7684\u51fd\u6570\uff0c\u90a3\u4e2a\u51fd\u6570\u5c06\u5728\u52a0\u8f7d\u6587\u4ef6\u540e\u7acb\u5373\u88ab\u8c03\u7528\u3002\u8be5\u51fd\u6570\u4e0d\u63a5\u6536\u4efb\u4f55\u53c2\u6570\uff0c\u5e94\u8be5\u8fd4\u56devoid\u3002\u76ee\u524d\u6ca1\u6709\u529e\u6cd5\u5378\u8f7d\u4e00\u4e2a\u52a8\u6001\u52a0\u8f7d\u7684\u6587\u4ef6\u3002

\n
\n
\n
\n
\n
\n

36.10.2. C \u8bed\u8a00\u51fd\u6570\u4e2d\u7684\u57fa\u7840\u7c7b\u578b

\n
\n
\n
\n

\u8981\u4e86\u89e3\u5982\u4f55\u7f16\u5199 C \u8bed\u8a00\u51fd\u6570\uff0c\u4f60\u9700\u8981\u4e86\u89e3 PostgreSQL\u5982\u4f55\u5728\u5185\u90e8\u8868\u8fbe\u57fa\u7840\u7c7b\u578b\u4ee5\u53ca\u5982\u4f55\u5c06\u5b83\u4eec\u4f20\u5165\u51fd\u6570\u548c\u4ece\u51fd\u6570\u4f20\u51fa\u3002\u5728\u5185\u90e8\uff0cPostgreSQL\u628a\u57fa\u7840\u7c7b\u578b\u89c6\u4e3a\u4e00\u5757\u201c\u5185\u5b58\u6570\u636e\u5757\u201d\u3002\u4f60\u4e3a\u8be5\u7c7b\u578b\u5b9a\u4e49\u7684\u7528\u6237\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u51b3\u5b9a\u4e86 PostgreSQL \u5982\u4f55\u64cd\u4f5c\u5b83\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cPostgreSQL \u53ea\u8d1f\u8d23\u628a\u6570\u636e\u5b58\u5230\u78c1\u76d8\u3001\u518d\u4ece\u78c1\u76d8\u53d6\u56de\uff0c\u800c\u6570\u636e\u7684\u8f93\u5165\u3001\u5904\u7406\u548c\u8f93\u51fa\u5219\u4f9d\u8d56\u4f60\u5b9a\u4e49\u7684\u8fd9\u4e9b\u51fd\u6570\u3002

\n

\u57fa\u7840\u7c7b\u578b\u53ef\u4ee5\u6709\u4e09\u79cd\u5185\u90e8\u683c\u5f0f\u4e4b\u4e00\uff1a

\n
\n
    \n
  • \n

    \u4f20\u503c\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u5b9a\u957f

    \n
    • \n
  • \n

    \u4f20\u5f15\u7528\uff0c\u53d8\u957f

    \n
    • \n
\n
\n

\u4f20\u503c\u7c7b\u578b\u5728\u957f\u5ea6\u4e0a\u53ea\u80fd\u662f 1\u30012 \u6216 4 \u5b57\u8282\uff08\u5982\u679c\u4f60\u7684\u673a\u5668\u4e0a sizeof(Datum)\u662f 8\uff0c\u5219\u8fd8\u6709 8 \u5b57\u8282\uff09\u3002\u4f60\u5e94\u5f53\u5c0f\u5fc3\u5730\u5b9a\u4e49\u4f60\u7684\u7c7b\u578b\u4ee5\u4fbf\u5b83\u4eec\u5728\u6240\u6709\u7684\u67b6\u6784\u4e0a\u90fd\u662f\u76f8\u540c\u7684\u5c3a\u5bf8\uff08\u5b57\u8282\uff09\u3002\u4f8b\u5982\uff0clong\u7c7b\u578b\u5f88\u5371\u9669\uff0c\u56e0\u4e3a\u5b83\u5728\u67d0\u4e9b\u673a\u5668\u4e0a\u662f 4 \u5b57\u8282\u4f46\u5728\u53e6\u5916\u4e00\u4e9b\u673a\u5668\u4e0a\u662f 8 \u5b57\u8282\uff0c\u800cint\u7c7b\u578b\u5728\u5927\u90e8\u5206 Unix \u673a\u5668\u4e0a\u90fd\u662f 4 \u5b57\u8282\u3002\u5728 Unix \u673a\u5668\u4e0aint4\u7c7b\u578b\u7684\u4e00\u79cd\u5408\u7406\u5b9e\u73b0\u53ef\u80fd\u662f\uff1a

\n
/* 4-byte integer, passed by value */\ntypedef int int4;\n
\n

\uff08\u5b9e\u9645\u7684 PostgreSQL C \u4ee3\u7801\u4f1a\u628a\u8fd9\u79cd\u7c7b\u578b\u79f0\u4e3aint32\uff0c\u56e0\u4e3a C \u4e2d\u7684\u4e60\u60ef\u662fintXX \u8868\u793aXX \u4f4d\u3002\u6ce8\u610f\u56e0\u6b64\u8fd8\u6709\u5c3a\u5bf8\u4e3a 1 \u5b57\u8282\u7684 C \u7c7b\u578bint8\u3002SQL \u7c7b\u578b int8\u5728 C \u4e2d\u88ab\u79f0\u4e3aint64\u3002\u53e6\u89c1\u8868\u00a036.2\uff09\u3002

\n

\u53e6\u4e00\u65b9\u9762\uff0c\u4efb\u610f\u5c3a\u5bf8\u7684\u5b9a\u957f\u7c7b\u578b\u90fd\u53ef\u4ee5\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u3002\u4f8b\u5982\uff0c\u8fd9\u91cc\u6709\u4e00\u79cd PostgreSQL\u7c7b\u578b\u7684\u5b9e\u73b0\u793a\u4f8b\uff1a

\n
/* 16-byte structure, passed by reference */\ntypedef struct\n{\n    double  x, y;\n} Point;\n
\n

\u5728PostgreSQL\u51fd\u6570\u4e2d\u4f20\u8fdb\u6216\u4f20\u51fa\u8fd9\u79cd\u7c7b\u578b\u65f6\uff0c\u53ea\u80fd\u4f7f\u7528\u6307\u5411\u8fd9\u79cd\u7c7b\u578b\u7684\u6307\u9488\u3002\u8981\u8fd4\u56de\u8fd9\u6837\u4e00\u79cd\u7c7b\u578b\u7684\u503c\uff0c\u7528 palloc\u5206\u914d\u6b63\u786e\u7684\u5185\u5b58\u91cf\uff0c\u7136\u540e\u586b\u5145\u5206\u914d\u597d\u7684\u5185\u5b58\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u8be5\u5185\u5b58\u7684\u6307\u9488\uff08\u8fd8\u6709\uff0c\u5982\u679c\u53ea\u60f3\u8fd4\u56de\u4e0e\u5177\u6709\u76f8\u540c\u6570\u636e\u7c7b\u578b\u7684\u4e00\u4e2a\u8f93\u5165\u53c2\u6570\u76f8\u540c\u7684\u503c\uff0c\u53ef\u4ee5\u8df3\u8fc7\u989d\u5916\u7684palloc\u5e76\u4e14\u8fd4\u56de\u6307\u5411\u8be5\u8f93\u5165\u503c\u7684\u6307\u9488\uff09\u3002

\n

\u6700\u540e\uff0c\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u4e5f\u4ee5\u5f15\u7528\u7684\u65b9\u5f0f\u4f20\u9012\u3002\u6240\u6709\u53d8\u957f\u7c7b\u578b\u5fc5\u987b\u7528\u4e00\u4e2a\u6b63\u597d 4 \u5b57\u8282\u7684\u4e0d\u900f\u660e\u957f\u5ea6\u5b57\u6bb5\u5f00\u59cb\uff0c\u8be5\u5b57\u6bb5\u4f1a\u7531SET_VARSIZE \u8bbe\u7f6e\uff0c\u7edd\u4e0d\u8981\u76f4\u63a5\u8bbe\u7f6e\u8be5\u5b57\u6bb5\uff01\u6240\u6709\u8981\u88ab\u5b58\u50a8\u5728\u8be5\u7c7b\u578b\u4e2d\u7684\u6570\u636e\u5fc5\u987b\u5728\u5185\u5b58\u4e2d\u63a5\u7740\u8be5\u957f\u5ea6\u5b57\u6bb5\u7684\u540e\u9762\u5b58\u50a8\u3002\u957f\u5ea6\u5b57\u6bb5\u5305\u542b\u8be5\u7ed3\u6784\u4f53\u7684\u603b\u957f\u5ea6\uff0c\u4e5f\u5c31\u662f\u5305\u62ec\u957f\u5ea6\u5b57\u6bb5\u672c\u8eab\u7684\u5c3a\u5bf8\u3002

\n

\u53e6\u4e00\u4e2a\u91cd\u70b9\u662f\u8981\u907f\u514d\u5728\u6570\u636e\u7c7b\u578b\u503c\u4e2d\u7559\u4e0b\u672a\u88ab\u521d\u59cb\u5316\u7684\u4f4d\u3002\u4f8b\u5982\uff0c\u8981\u6ce8\u610f\u628a\u53ef\u80fd\u5b58\u5728\u4e8e\u7ed3\u6784\u4f53\u4e2d\u7684\u4efb\u4f55\u5bf9\u9f50\u586b\u5145\u5b57\u8282\u7f6e\u96f6\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u4f60\u7684\u6570\u636e\u7c7b\u578b\u7684\u903b\u8f91\u7b49\u4ef7\u5e38\u91cf\u53ef\u80fd\u4f1a\u88ab\u89c4\u5212\u5668\u8ba4\u4e3a\u662f\u4e0d\u7b49\u7684\uff0c\u8fdb\u800c\u5bfc\u81f4\u4f4e\u6548\u7684\uff08\u4e0d\u8fc7\u8fd8\u662f\u6b63\u786e\u7684\uff09\u8ba1\u5212\u3002

\n
\n

\u8b66\u544a

\n

\u7edd\u4e0d\u8981\u4fee\u6539\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u7684\u8f93\u5165\u503c\u7684\u5185\u5bb9\u3002\u5982\u679c\u8fd9\u6837\u505a\u5f88\u53ef\u80fd\u4f1a\u7834\u574f\u78c1\u76d8\u4e0a\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u7ed9\u51fa\u7684\u6307\u9488\u53ef\u80fd\u76f4\u63a5\u6307\u5411\u4e00\u4e2a\u78c1\u76d8\u7f13\u51b2\u533a\u3002\u8fd9\u6761\u89c4\u5219\u552f\u4e00\u7684\u4f8b\u5916\u5728\u7b2c\u00a036.12\u00a0\u8282\u4e2d\u6709\u89e3\u91ca\u3002

\n
\n

\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\u7c7b\u578btext\uff1a

\n
typedef struct {\n    int32 length;\n    char data[FLEXIBLE_ARRAY_MEMBER];\n} text;\n
\n

[FLEXIBLE_ARRAY_MEMBER]\u8bb0\u53f7\u8868\u793a\u6570\u636e\u90e8\u5206\u7684\u5b9e\u9645\u957f\u5ea6\u4e0d\u7531\u8be5\u58f0\u660e\u6307\u5b9a\u3002

\n

\u5728\u64cd\u4f5c\u53d8\u957f\u7c7b\u578b\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u5c0f\u5fc3\u5206\u914d\u6b63\u786e\u6570\u91cf\u7684\u5185\u5b58\uff0c\u5e76\u6b63\u786e\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u5728\u4e00\u4e2atext\u7ed3\u6784\u4f53\u4e2d\u5b58\u50a8 40 \u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u4ee3\u7801\u7247\u6bb5\uff1a

\n
#include \"postgres.h\"\n...\nchar buffer[40]; /* our source data */\n...\ntext *destination = (text *) palloc(VARHDRSZ + 40);\nSET_VARSIZE(destination, VARHDRSZ + 40);\nmemcpy(destination->data, buffer, 40);\n...\n\n
\n

VARHDRSZ\u548csizeof(int32)\u4e00\u6837\uff0c\u4f46\u662f\u7528\u5b8fVARHDRSZ\u6765\u5f15\u7528\u53d8\u957f\u7c7b\u578b\u7684\u989d\u5916\u5f00\u9500\u7684\u5c3a\u5bf8\u88ab\u8ba4\u4e3a\u662f\u6bd4\u8f83\u597d\u7684\u98ce\u683c\u3002\u8fd8\u6709\uff0c\u5fc5\u987b\u4f7f\u7528SET_VARSIZE\u5b8f\u6765\u8bbe\u7f6e\u957f\u5ea6\u5b57\u6bb5\uff0c\u800c\u4e0d\u662f\u7528\u7b80\u5355\u7684\u8d4b\u503c\u6765\u8bbe\u7f6e\u3002

\n

\u8868\u00a036.2\u5c55\u793a\u4e86 PostgreSQL \u4e2d\u8bb8\u591a\u5185\u7f6e SQL \u6570\u636e\u7c7b\u578b\u6240\u5bf9\u5e94\u7684 C \u7c7b\u578b\u3002\u201c\u5b9a\u4e49\u6587\u4ef6\u201d\u5217\u7ed9\u51fa\u4e86\u9700\u8981\u5305\u542b\u7684\u5934\u6587\u4ef6\uff0c\u4ee5\u83b7\u53d6\u7c7b\u578b\u5b9a\u4e49\u3002\uff08\u5b9e\u9645\u7684\u5b9a\u4e49\u53ef\u80fd\u4f4d\u4e8e\u6240\u5217\u6587\u4ef6\u5305\u542b\u7684\u5176\u4ed6\u6587\u4ef6\u4e2d\u3002\u5efa\u8bae\u7528\u6237\u575a\u6301\u4f7f\u7528\u5df2\u5b9a\u4e49\u7684\u63a5\u53e3\u3002\uff09\u8bf7\u6ce8\u610f\uff0c\u5728\u670d\u52a1\u5668\u4ee3\u7801\u7684\u4efb\u4f55\u6e90\u6587\u4ef6\u4e2d\uff0c\u90fd\u5e94\u8be5\u59cb\u7ec8\u9996\u5148\u5305\u542bpostgres.h\uff0c\u56e0\u4e3a\u5b83\u58f0\u660e\u4e86\u5f88\u591a\u4f60\u53cd\u6b63\u90fd\u4f1a\u7528\u5230\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u5148\u5305\u542b\u5176\u4ed6\u5934\u6587\u4ef6\u53ef\u80fd\u4f1a\u5e26\u6765\u53ef\u79fb\u690d\u6027\u95ee\u9898\u3002

\n
\n

\u8868\u00a036.2.\u00a0\u5185\u7f6e SQL \u7c7b\u578b\u7b49\u6548\u7684 C \u7c7b\u578b

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
SQL \u7c7b\u578bC \u7c7b\u578b\u5b9a\u4e49\u6587\u4ef6
booleanboolpostgres.h\uff08\u53ef\u80fd\u662f\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
boxBOX*utils/geo_decls.h
byteabytea*postgres.h
\"char\"char\uff08\u7f16\u8bd1\u5668\u5185\u7f6e\uff09
characterBpChar*postgres.h
cidCommandIdpostgres.h
dateDateADTutils/date.h
float4 (real)float4postgres.h
float8 (double precision)float8postgres.h
int2 (smallint)int16postgres.h
int4 (integer)int32postgres.h
int8 (bigint)int64postgres.h
intervalInterval*datatype/timestamp.h
lsegLSEG*utils/geo_decls.h
nameNamepostgres.h
numeric\u6570\u503cutils/numeric.h
oidOidpostgres.h
oidvectoroidvector*postgres.h
pathPATH*utils/geo_decls.h
pointPOINT*utils/geo_decls.h
regprocRegProcedurepostgres.h
\u6587\u672ctext*postgres.h
tidItemPointerstorage/itemptr.h
timeTimeADTutils/date.h
time with time zoneTimeTzADTutils/date.h
timestampTimestampdatatype/timestamp.h
timestamp with time zoneTimestampTzdatatype/timestamp.h
varcharVarChar*postgres.h
xidTransactionIdpostgres.h
\n
\n

\n

\u4e86\u89e3\u4e86\u57fa\u7840\u7c7b\u578b\u6240\u6709\u53ef\u80fd\u7684\u7ed3\u6784\u540e\uff0c\u5c31\u53ef\u4ee5\u770b\u4e00\u4e9b\u5b9e\u9645\u51fd\u6570\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.3. \u7248\u672c 1 \u7684\u8c03\u7528\u7ea6\u5b9a

\n
\n
\n
\n

\u7248\u672c-1 \u7684\u8c03\u7528\u7ea6\u5b9a\u4f9d\u8d56\u4e8e\u5b8f\u6765\u5c4f\u853d\u4f20\u9012\u53c2\u6570\u548c\u7ed3\u679c\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u7248\u672c-1 \u51fd\u6570\u7684 C \u58f0\u660e\u603b\u662f\uff1a

\n
Datum funcname(PG_FUNCTION_ARGS)\n
\n

\u6b64\u5916\uff0c\u5b8f\u8c03\u7528\uff1a

\n
PG_FUNCTION_INFO_V1(funcname);\n
\n

\u5fc5\u987b\u51fa\u73b0\u5728\u540c\u4e00\u4e2a\u6e90\u6587\u4ef6\u4e2d\uff08\u6309\u60ef\u4f8b\u4f1a\u6b63\u597d\u5199\u5728\u8be5\u51fd\u6570\u672c\u8eab\u4e4b\u524d\uff09\u3002\u8fd9\u79cd\u5b8f\u8c03\u7528\u4e0d\u662finternal\u8bed\u8a00\u51fd\u6570\u6240\u9700\u8981\u7684\uff0c\u56e0\u4e3a PostgreSQL\u4f1a\u5047\u5b9a\u6240\u6709\u5185\u90e8\u51fd\u6570\u90fd\u4f7f\u7528\u7248\u672c-1 \u8c03\u7528\u7ea6\u5b9a\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u52a8\u6001\u8f7d\u5165\u51fd\u6570\u662f\u5fc5\u9700\u7684\u3002

\n

\u5728\u7248\u672c-1 \u51fd\u6570\u4e2d\uff0c\u6bcf\u4e00\u4e2a\u5b9e\u53c2\u90fd\u4f7f\u7528\u5bf9\u5e94\u4e8e\u8be5\u53c2\u6570\u6570\u636e\u7c7b\u578b\u7684PG_GETARG_xxx()\u5b8f\u53d6\u5f97\u3002\uff08\u5728\u975e\u4e25\u683c\u7684\u51fd\u6570\u4e2d\uff0c\u9700\u8981\u4f7f\u7528PG_ARGISNULL()\u5bf9\u53c2\u6570\u662f\u5426\u4e3a\u7a7a\u503c\u63d0\u524d\u505a\u68c0\u67e5\uff1b\u89c1\u4e0b\u6587\u3002\uff09\u7ed3\u679c\u8981\u7528\u5bf9\u5e94\u4e8e\u8fd4\u56de\u7c7b\u578b\u7684PG_RETURN_xxx()\u5b8f\u8fd4\u56de\u3002PG_GETARG_xxx()\u7684\u53c2\u6570\u662f\u8981\u53d6\u5f97\u7684\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002PG_RETURN_xxx()\u7684\u53c2\u6570\u662f\u5b9e\u9645\u8981\u8fd4\u56de\u7684\u503c\u3002

\n

\u8981\u8c03\u7528\u53e6\u4e00\u4e2a\u7248\u672c-1 \u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528 DirectFunctionCalln(func, arg1, ..., argn)\u3002\u8fd9\u5728\u4f60\u60f3\u8c03\u7528\u6807\u51c6\u5185\u90e8\u5e93\u4e2d\u5b9a\u4e49\u7684\u51fd\u6570\u65f6\u5c24\u5176\u6709\u7528\uff0c\u56e0\u4e3a\u5b83\u63d0\u4f9b\u4e86\u4e0e\u5176 SQL \u7b7e\u540d\u76f8\u4f3c\u7684\u63a5\u53e3\u3002

\n

\u8fd9\u4e9b\u4fbf\u5229\u51fd\u6570\u4ee5\u53ca\u7c7b\u4f3c\u51fd\u6570\u90fd\u53ef\u4ee5\u5728 fmgr.h \u4e2d\u627e\u5230\u3002DirectFunctionCalln \u7cfb\u5217\u628a C \u51fd\u6570\u540d\u4f5c\u4e3a\u5176\u7b2c\u4e00\u4e2a\u53c2\u6570\u3002\u53e6\u6709 OidFunctionCalln \u7b49\u4e00\u4e9b\u53d8\u4f53\uff0c\u5b83\u4eec\u63a5\u6536\u76ee\u6807\u51fd\u6570\u7684 OID\u3002\u6240\u6709\u8fd9\u4e9b\u51fd\u6570\u90fd\u8981\u6c42\u4ee5 Datum \u5f62\u5f0f\u63d0\u4f9b\u51fd\u6570\u53c2\u6570\uff0c\u8fd4\u56de\u503c\u4e5f\u540c\u6837\u662f Datum\u3002\u6ce8\u610f\uff0c\u4f7f\u7528\u8fd9\u4e9b\u4fbf\u5229\u51fd\u6570\u65f6\uff0c\u53c2\u6570\u548c\u7ed3\u679c\u90fd\u4e0d\u80fd\u4e3a NULL\u3002

\n

\u4f8b\u5982\uff0c\u8981\u5728 C \u4e2d\u8c03\u7528 starts_with(text, text)\uff0c\u4f60\u53ef\u4ee5\u5728\u7cfb\u7edf\u76ee\u5f55\u4e2d\u67e5\u5230\u5b83\u7684 C \u5b9e\u73b0\u662f Datum text_starts_with(PG_FUNCTION_ARGS) \u51fd\u6570\u3002\u901a\u5e38\u4f60\u4f1a\u7528 DirectFunctionCall2(text_starts_with, ...) \u6765\u8c03\u7528\u5b83\u3002\u4e0d\u8fc7\uff0cstarts_with(text, text) \u9700\u8981\u6392\u5e8f\u89c4\u5219\u4fe1\u606f\uff0c\u56e0\u6b64\u5982\u679c\u8fd9\u6837\u8c03\u7528\uff0c\u4f1a\u56e0\u201c\u65e0\u6cd5\u786e\u5b9a\u5b57\u7b26\u4e32\u6bd4\u8f83\u8be5\u4f7f\u7528\u54ea\u4e00\u79cd\u6392\u5e8f\u89c4\u5219\u201d\u800c\u5931\u8d25\u3002\u4f60\u5fc5\u987b\u6539\u7528 DirectFunctionCall2Coll(text_starts_with, ...)\uff0c\u5e76\u63d0\u4f9b\u6240\u9700\u7684\u6392\u5e8f\u89c4\u5219\uff0c\u901a\u5e38\u5c31\u662f\u4ece PG_GET_COLLATION() \u4f20\u9012\u8fdb\u6765\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u6240\u793a\u3002

\n

fmgr.h \u8fd8\u63d0\u4f9b\u4e86\u4fbf\u4e8e\u5728 C \u7c7b\u578b\u548c Datum \u4e4b\u95f4\u8f6c\u6362\u7684\u5b8f\u3002\u4f8b\u5982\uff0c\u8981\u628a Datum \u8f6c\u6210 text*\uff0c\u53ef\u4ee5\u4f7f\u7528 DatumGetTextPP(X)\u3002\u867d\u7136\u67d0\u4e9b\u7c7b\u578b\u4e3a\u53cd\u5411\u8f6c\u6362\u63d0\u4f9b\u4e86\u540d\u4e3a TypeGetDatum(X) \u4e4b\u7c7b\u7684\u5b8f\uff0c\u4f46 text* \u6ca1\u6709\uff1b\u5bf9\u5b83\u800c\u8a00\uff0c\u76f4\u63a5\u4f7f\u7528\u901a\u7528\u5b8f PointerGetDatum(X) \u5373\u53ef\u3002\u5982\u679c\u4f60\u7684\u6269\u5c55\u5b9a\u4e49\u4e86\u989d\u5916\u7684\u7c7b\u578b\uff0c\u901a\u5e38\u4e5f\u5f88\u65b9\u4fbf\u4e3a\u8fd9\u4e9b\u7c7b\u578b\u5b9a\u4e49\u7c7b\u4f3c\u7684\u5b8f\u3002

\n

\u4ee5\u4e0b\u662f\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\u7684\u4e00\u4e9b\u793a\u4f8b\uff1a

\n
#include \"postgres.h\"\n#include <string.h>\n#include \"fmgr.h\"\n#include \"utils/geo_decls.h\"\n#include \"varatt.h\"\n\nPG_MODULE_MAGIC;\n\n/* by value */\n\nPG_FUNCTION_INFO_V1(add_one);\n\nDatum\nadd_one(PG_FUNCTION_ARGS)\n{\n    int32   arg = PG_GETARG_INT32(0);\n\n    PG_RETURN_INT32(arg + 1);\n}\n\n/* by reference, fixed length */\n\nPG_FUNCTION_INFO_V1(add_one_float8);\n\nDatum\nadd_one_float8(PG_FUNCTION_ARGS)\n{\n    /* The macros for FLOAT8 hide its pass-by-reference nature. */\n    float8   arg = PG_GETARG_FLOAT8(0);\n\n    PG_RETURN_FLOAT8(arg + 1.0);\n}\n\nPG_FUNCTION_INFO_V1(makepoint);\n\nDatum\nmakepoint(PG_FUNCTION_ARGS)\n{\n    /* Here, the pass-by-reference nature of Point is not hidden. */\n    Point     *pointx = PG_GETARG_POINT_P(0);\n    Point     *pointy = PG_GETARG_POINT_P(1);\n    Point     *new_point = (Point *) palloc(sizeof(Point));\n\n    new_point->x = pointx->x;\n    new_point->y = pointy->y;\n\n    PG_RETURN_POINT_P(new_point);\n}\n\n/* by reference, variable length */\n\nPG_FUNCTION_INFO_V1(copytext);\n\nDatum\ncopytext(PG_FUNCTION_ARGS)\n{\n    text     *t = PG_GETARG_TEXT_PP(0);\n\n    /*\n     * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the\n     * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a\n     * full-length header.\n     */\n    text     *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n    SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);\n\n    /*\n     * VARDATA is a pointer to the data region of the new struct.  The source\n     * could be a short datum, so retrieve its data through VARDATA_ANY.\n     */\n    memcpy(VARDATA(new_t),          /* destination */\n           VARDATA_ANY(t),          /* source */\n           VARSIZE_ANY_EXHDR(t));   /* how many bytes */\n    PG_RETURN_TEXT_P(new_t);\n}\n\nPG_FUNCTION_INFO_V1(concat_text);\n\nDatum\nconcat_text(PG_FUNCTION_ARGS)\n{\n    text  *arg1 = PG_GETARG_TEXT_PP(0);\n    text  *arg2 = PG_GETARG_TEXT_PP(1);\n    int32 arg1_size = VARSIZE_ANY_EXHDR(arg1);\n    int32 arg2_size = VARSIZE_ANY_EXHDR(arg2);\n    int32 new_text_size = arg1_size + arg2_size + VARHDRSZ;\n    text *new_text = (text *) palloc(new_text_size);\n\n    SET_VARSIZE(new_text, new_text_size);\n    memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);\n    memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);\n    PG_RETURN_TEXT_P(new_text);\n}\n\n/* A wrapper around starts_with(text, text) */\n\nPG_FUNCTION_INFO_V1(t_starts_with);\n\nDatum\nt_starts_with(PG_FUNCTION_ARGS)\n{\n    text       *t1 = PG_GETARG_TEXT_PP(0);\n    text       *t2 = PG_GETARG_TEXT_PP(1);\n    Oid         collid = PG_GET_COLLATION();\n    bool        result;\n\n    result = DatumGetBool(DirectFunctionCall2Coll(text_starts_with,\n                                                  collid,\n                                                  PointerGetDatum(t1),\n                                                  PointerGetDatum(t2)));\n    PG_RETURN_BOOL(result);\n}\n\n
\n

\u5047\u5b9a\u4e0a\u8ff0\u4ee3\u7801\u5df2\u7ecf\u51c6\u5907\u5728\u6587\u4ef6funcs.c\u4e2d\u5e76\u4e14\u88ab\u7f16\u8bd1\u6210\u4e00\u4e2a\u5171\u4eab\u5bf9\u8c61\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u8fd9\u6837\u7684\u547d\u4ee4\u5728PostgreSQL\u4e2d\u5b9a\u4e49\u51fd\u6570\uff1a

\n
CREATE FUNCTION add_one(integer) RETURNS integer\n     AS 'DIRECTORY/funcs', 'add_one'\n     LANGUAGE C STRICT;\n\n-- note overloading of SQL function name \"add_one\"\nCREATE FUNCTION add_one(double precision) RETURNS double precision\n     AS 'DIRECTORY/funcs', 'add_one_float8'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION makepoint(point, point) RETURNS point\n     AS 'DIRECTORY/funcs', 'makepoint'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION copytext(text) RETURNS text\n     AS 'DIRECTORY/funcs', 'copytext'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION concat_text(text, text) RETURNS text\n     AS 'DIRECTORY/funcs', 'concat_text'\n     LANGUAGE C STRICT;\n\nCREATE FUNCTION t_starts_with(text, text) RETURNS boolean\n     AS 'DIRECTORY/funcs', 't_starts_with'\n     LANGUAGE C STRICT;\n
\n

\u8fd9\u91cc\uff0cDIRECTORY \u8868\u793a\u5171\u4eab\u5e93\u6587\u4ef6\u6240\u5728\u76ee\u5f55\uff0c\u4f8b\u5982 PostgreSQL \u6559\u7a0b\u76ee\u5f55\uff0c\u5176\u4e2d\u5305\u542b\u672c\u8282\u793a\u4f8b\u7684\u4ee3\u7801\u3002\uff08\u66f4\u597d\u7684\u5199\u6cd5\u662f\u5148\u5c06 DIRECTORY \u52a0\u5165\u641c\u7d22\u8def\u5f84\uff0c\u518d\u5728 AS \u5b50\u53e5\u4e2d\u4ec5\u5199 'funcs'\u3002\u65e0\u8bba\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u53ef\u4ee5\u7701\u7565\u5171\u4eab\u5e93\u7684\u5e73\u53f0\u7279\u5b9a\u6269\u5c55\u540d\uff0c\u901a\u5e38\u4e3a .so\u3002\uff09

\n

\u6ce8\u610f\u6211\u4eec\u5df2\u7ecf\u628a\u51fd\u6570\u6307\u5b9a\u4e3a\u201cstrict\u201d\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u6709\u4efb\u4f55\u8f93\u5165\u503c\u4e3a\u7a7a\u503c\uff0c\u7cfb\u7edf\u5e94\u8be5\u81ea\u52a8\u5047\u5b9a\u7ed3\u679c\u4e3a\u7a7a\u503c\u3002\u901a\u8fc7\u8fd9\u79cd\u505a\u6cd5\uff0c\u6211\u4eec\u907f\u514d\u5728\u51fd\u6570\u4ee3\u7801\u4e2d\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002\u5982\u679c\u4e0d\u8fd9\u6837\u505a\uff0c\u6211\u4eec\u5fc5\u987b\u4f7f\u7528PG_ARGISNULL()\u660e\u786e\u5730\u68c0\u67e5\u7a7a\u503c\u8f93\u5165\u3002

\n

\u5b8fPG_ARGISNULL(n)\u5141\u8bb8\u4e00\u4e2a\u51fd\u6570\u6d4b\u8bd5\u662f\u5426\u6bcf\u4e00\u4e2a\u8f93\u5165\u4e3a\u7a7a\u503c\uff08\u5f53\u7136\uff0c\u53ea\u9700\u8981\u5728\u6ca1\u6709\u58f0\u660e\u4e3a\u201cstrict\u201d\u7684\u51fd\u6570\u4e2d\u8fd9\u6837\u505a\uff09\u3002\u548cPG_GETARG_xxx()\u5b8f\u4e00\u6837\uff0c\u8f93\u5165\u53c2\u6570\u4e5f\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u6570\u3002\u6ce8\u610f\u5e94\u8be5\u5728\u9a8c\u8bc1\u4e86\u4e00\u4e2a\u53c2\u6570\u4e0d\u662f\u7a7a\u503c\u4e4b\u540e\u624d\u6267\u884cPG_GETARG_xxx()\u3002\u8981\u8fd4\u56de\u7a7a\u503c\u7ed3\u679c\uff0c\u5e94\u6267\u884cPG_RETURN_NULL()\uff0c\u5b83\u5bf9\u4e25\u683c\u7684\u4ee5\u53ca\u975e\u4e25\u683c\u7684\u51fd\u6570\u90fd\u6709\u7528\u3002

\n

\u4e4d\u770b\u4e4b\u4e0b\uff0c\u4e0e\u666e\u901a\u7684 C \u8c03\u7528\u7ea6\u5b9a\u76f8\u6bd4\uff0c\u7248\u672c 1 \u7684\u7f16\u7801\u7ea6\u5b9a\u4f3c\u4e4e\u53ea\u662f\u589e\u52a0\u4e86\u590d\u6742\u5ea6\u3002\u4e0d\u8fc7\uff0c\u5b83\u4eec\u786e\u5b9e\u8ba9\u6211\u4eec\u80fd\u591f\u5904\u7406\u53ef\u4e3a NULL \u7684\u53c2\u6570\u548c\u8fd4\u56de\u503c\uff0c\u4ee5\u53ca\u201c\u7ecf\u8fc7 TOAST \u5904\u7406\u201d\uff08\u538b\u7f29\u6216\u884c\u5916\uff09\u7684\u503c\u3002

\n

\u7248\u672c 1 \u63a5\u53e3\u8fd8\u63d0\u4f9b\u4e86\u4e24\u79cd PG_GETARG_xxx() \u5b8f\u53d8\u4f53\u3002\u7b2c\u4e00\u79cd PG_GETARG_xxx_COPY() \u4fdd\u8bc1\u8fd4\u56de\u6307\u5b9a\u53c2\u6570\u7684\u53ef\u5199\u526f\u672c\u3002\u666e\u901a\u5b8f\u6709\u65f6\u4f1a\u8fd4\u56de\u6307\u5411\u8868\u4e2d\u7269\u7406\u5b58\u50a8\u503c\u7684\u6307\u9488\uff0c\u7981\u6b62\u5199\u5165\uff1b\u4f7f\u7528 PG_GETARG_xxx_COPY() \u5219\u53ef\u4fdd\u8bc1\u7ed3\u679c\u53ef\u5199\u3002\u7b2c\u4e8c\u79cd\u662f\u63a5\u53d7\u4e09\u4e2a\u53c2\u6570\u7684 PG_GETARG_xxx_SLICE() \u5b8f\uff1a\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u51fd\u6570\u53c2\u6570\u7684\u7f16\u53f7\uff0c\u5982\u4e0a\u6587\u6240\u8ff0\uff1b\u7b2c\u4e8c\u3001\u4e09\u4e2a\u53c2\u6570\u5206\u522b\u662f\u8981\u8fd4\u56de\u7247\u6bb5\u7684\u504f\u79fb\u91cf\u548c\u957f\u5ea6\u3002\u504f\u79fb\u91cf\u4ece\u96f6\u5f00\u59cb\uff0c\u8d1f\u957f\u5ea6\u8868\u793a\u8fd4\u56de\u8be5\u503c\u7684\u5269\u4f59\u90e8\u5206\u3002\u5bf9\u4e8e\u5b58\u50a8\u7c7b\u578b\u4e3a external \u7684\u5927\u503c\uff0c\u8fd9\u4e9b\u5b8f\u53ef\u66f4\u9ad8\u6548\u5730\u8bbf\u95ee\u5176\u4e2d\u4e00\u90e8\u5206\u3002\u5217\u7684\u5b58\u50a8\u7c7b\u578b\u53ef\u901a\u8fc7 ALTER TABLE tablename ALTER COLUMN colname SET STORAGE storagetype \u6307\u5b9a\uff0c\u5176\u4e2d storagetype \u4e3a plain\u3001external\u3001extended \u6216 main \u4e4b\u4e00\u3002

\n

\u6700\u540e\uff0c\u7248\u672c-1 \u7684\u51fd\u6570\u8c03\u7528\u7ea6\u5b9a\u53ef\u4ee5\u8fd4\u56de\u96c6\u5408\u7ed3\u679c\uff08\u7b2c\u00a036.10.9\u00a0\u8282\uff09\u3001\u5b9e\u73b0\u89e6\u53d1\u5668\u51fd\u6570\uff08\u7b2c\u00a037\u00a0\u7ae0\uff09\u548c\u8fc7\u7a0b\u8bed\u8a00\u8c03\u7528\u5904\u7406\u5668\uff08\u7b2c\u00a057\u00a0\u7ae0\uff09\u3002\u66f4\u591a\u7ec6\u8282\u53ef\u89c1\u6e90\u4ee3\u7801\u53d1\u5e03\u4e2d\u7684src/backend/utils/fmgr/README\u3002

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36.10.4. \u7f16\u5199\u4ee3\u7801

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\u5728\u5f00\u59cb\u66f4\u9ad8\u7ea7\u7684\u8bdd\u9898\u4e4b\u524d\uff0c\u6211\u4eec\u5e94\u8be5\u8ba8\u8bba\u4e00\u4e0b\u7528\u4e8e PostgreSQL C \u8bed\u8a00\u51fd\u6570\u7684\u7f16\u7801\u89c4\u5219\u3002\u867d\u7136\u6709\u53ef\u80fd\u628a\u4e0d\u662f C \u7f16\u5199\u7684\u51fd\u6570\u8f7d\u5165\u5230 PostgreSQL\u4e2d\uff0c\u4f46\u5373\u4f7f\u80fd\u591f\u505a\u5230\uff0c\u901a\u5e38\u4e5f\u5f88\u56f0\u96be\uff0c\u56e0\u4e3a\u5176\u4ed6\u8bed\u8a00\uff08\u4f8b\u5982 C++\u3001FORTRAN \u6216\u8005 Pascal\uff09\u901a\u5e38\u4e0d\u4f1a\u9075\u5faa\u548c C \u76f8\u540c\u7684\u8c03\u7528\u7ea6\u5b9a\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5176\u4ed6\u8bed\u8a00\u4e0d\u4f1a\u4ee5\u540c\u6837\u7684\u65b9\u5f0f\u5728\u51fd\u6570\u4e4b\u95f4\u4f20\u9012\u53c2\u6570\u4ee5\u53ca\u8fd4\u56de\u503c\u3002\u7531\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0c\u6211\u4eec\u4f1a\u5047\u5b9a\u4f60\u7684 C \u8bed\u8a00\u51fd\u6570\u786e\u5b9e\u662f\u7528 C \u7f16\u5199\u7684\u3002

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\u7f16\u5199\u548c\u6784\u5efa C \u8bed\u8a00\u51fd\u6570\u7684\u57fa\u672c\u89c4\u5219\u5982\u4e0b\uff1a

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  • \n

    \u4f7f\u7528 pg_config --includedir-server \u67e5\u51fa PostgreSQL \u670d\u52a1\u5668\u5934\u6587\u4ef6\u5728\u4f60\u7684\u7cfb\u7edf\u4e0a\uff08\u6216\u4f60\u7684\u7528\u6237\u5c06\u8981\u8fd0\u884c\u7684\u7cfb\u7edf\u4e0a\uff09\u5b89\u88c5\u4e8e\u4f55\u5904\u3002

    \n
    • \n
  • \n

    \u4e3a\u4e86\u8ba9\u4f60\u7684\u4ee3\u7801\u80fd\u591f\u88ab PostgreSQL \u52a8\u6001\u88c5\u5165\uff0c\u7f16\u8bd1\u548c\u94fe\u63a5\u65f6\u603b\u662f\u9700\u8981\u7279\u6b8a\u7684\u9009\u9879\u3002\u5173\u4e8e\u5982\u4f55\u5728\u7279\u5b9a\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u5b8c\u6210\u8fd9\u4ef6\u4e8b\uff0c\u8be6\u89c1\u7b2c\u00a036.10.5\u00a0\u8282\u3002

    \n
    • \n
  • \n

    \u8bb0\u5f97\u6309\u7167\u7b2c\u00a036.10.1\u00a0\u8282\u4e2d\u7684\u8bf4\u660e\uff0c\u4e3a\u4f60\u7684\u5171\u4eab\u5e93\u5b9a\u4e49\u4e00\u4e2a\u201c\u9b54\u6570\u5757\u201d\u3002

    \n
    • \n
  • \n

    \u5206\u914d\u5185\u5b58\u65f6\uff0c\u4f7f\u7528 PostgreSQL \u63d0\u4f9b\u7684 palloc \u548c pfree\uff0c\u800c\u4e0d\u662f\u76f8\u5e94\u7684 C \u5e93\u51fd\u6570 malloc \u548c free\u3002\u7528 palloc \u5206\u914d\u7684\u5185\u5b58\u4f1a\u5728\u6bcf\u4e2a\u4e8b\u52a1\u7ed3\u675f\u65f6\u81ea\u52a8\u91ca\u653e\uff0c\u4ece\u800c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u3002

    \n
    • \n
  • \n

    \u603b\u662f\u4f7f\u7528 memset \u5c06\u7ed3\u6784\u4f53\u7684\u6240\u6709\u5b57\u8282\u6e05\u96f6\uff08\u6216\u8005\u4e00\u5f00\u59cb\u5c31\u7528 palloc0 \u6765\u5206\u914d\u5b83\u4eec\uff09\u3002\u5373\u4f7f\u4f60\u7ed9\u7ed3\u6784\u4f53\u7684\u6bcf\u4e2a\u5b57\u6bb5\u90fd\u8d4b\u4e86\u503c\uff0c\u7ed3\u6784\u4f53\u4e2d\u4ecd\u53ef\u80fd\u5b58\u5728\u5305\u542b\u5783\u573e\u503c\u7684\u5bf9\u9f50\u586b\u5145\u5b57\u8282\uff08\u4e5f\u5c31\u662f\u7ed3\u6784\u4f53\u4e2d\u7684\u7a7a\u6d1e\uff09\u3002\u5982\u679c\u4e0d\u8fd9\u4e48\u505a\uff0c\u5c31\u5f88\u96be\u652f\u6301 hash \u7d22\u5f15\u6216\u54c8\u5e0c\u8fde\u63a5\uff0c\u56e0\u4e3a\u90a3\u65f6\u4f60\u5fc5\u987b\u53ea\u6311\u51fa\u6570\u636e\u7ed3\u6784\u4e2d\u771f\u6b63\u6709\u610f\u4e49\u7684\u4f4d\u6765\u8ba1\u7b97 hash \u503c\u3002\u89c4\u5212\u5668\u6709\u65f6\u4e5f\u4f9d\u8d56\u6309\u4f4d\u76f8\u7b49\u6765\u6bd4\u8f83\u5e38\u91cf\uff0c\u56e0\u6b64\u5982\u679c\u903b\u8f91\u4e0a\u7b49\u4ef7\u7684\u503c\u5728\u6309\u4f4d\u4e0a\u4e0d\u76f8\u7b49\uff0c\u5c31\u53ef\u80fd\u5f97\u5230\u4e0d\u7406\u60f3\u7684\u89c4\u5212\u7ed3\u679c\u3002

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    • \n
  • \n

    PostgreSQL \u7684\u5927\u591a\u6570\u5185\u90e8\u7c7b\u578b\u90fd\u5728 postgres.h \u4e2d\u58f0\u660e\uff0c\u800c\u51fd\u6570\u7ba1\u7406\u5668\u63a5\u53e3\uff08PG_FUNCTION_ARGS \u7b49\uff09\u4f4d\u4e8e fmgr.h \u4e2d\uff0c\u56e0\u6b64\u81f3\u5c11\u9700\u8981\u5305\u542b\u8fd9\u4e24\u4e2a\u6587\u4ef6\u3002\u51fa\u4e8e\u53ef\u79fb\u690d\u6027\u8003\u8651\uff0c\u6700\u597d\u628a postgres.h \u653e\u5728\u6700\u524d\u9762\uff0c\u5148\u4e8e\u4efb\u4f55\u5176\u4ed6\u7cfb\u7edf\u6216\u7528\u6237\u5934\u6587\u4ef6\u3002\u5305\u542b postgres.h \u65f6\uff0c\u4e5f\u4f1a\u987a\u5e26\u4e3a\u4f60\u5305\u542b elog.h \u548c palloc.h\u3002

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    • \n
  • \n

    \u76ee\u6807\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u540d\u4e0d\u80fd\u5f7c\u6b64\u51b2\u7a81\uff0c\u4e5f\u4e0d\u80fd\u4e0e PostgreSQL \u670d\u52a1\u5668\u53ef\u6267\u884c\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u7b26\u53f7\u51b2\u7a81\u3002\u5982\u679c\u4f60\u6536\u5230\u8fd9\u7c7b\u9519\u8bef\u6d88\u606f\uff0c\u5c31\u5fc5\u987b\u91cd\u547d\u540d\u76f8\u5173\u51fd\u6570\u6216\u53d8\u91cf\u3002

    \n
    • \n
\n
\n
\n
\n
\n
\n
\n

36.10.5. \u7f16\u8bd1\u548c\u94fe\u63a5\u52a8\u6001\u88c5\u8f7d\u51fd\u6570

\n
\n
\n
\n

\u5728\u4f60\u80fd\u591f\u4f7f\u7528\u4ee5 C \u7f16\u5199\u7684 PostgreSQL \u6269\u5c55\u51fd\u6570\u4e4b\u524d\uff0c\u5fc5\u987b\u4ee5\u7279\u6b8a\u65b9\u5f0f\u5bf9\u5b83\u4eec\u8fdb\u884c\u7f16\u8bd1\u548c\u94fe\u63a5\uff0c\u4ee5\u751f\u6210\u4e00\u4e2a\u53ef\u7531\u670d\u52a1\u5668\u52a8\u6001\u88c5\u8f7d\u7684\u6587\u4ef6\u3002\u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u9700\u8981\u521b\u5efa\u4e00\u4e2a\u5171\u4eab\u5e93\u3002

\n

\u82e5\u60f3\u4e86\u89e3\u672c\u8282\u672a\u6db5\u76d6\u7684\u4fe1\u606f\uff0c\u4f60\u5e94\u9605\u8bfb\u64cd\u4f5c\u7cfb\u7edf\u7684\u6587\u6863\uff0c\u7279\u522b\u662f C \u7f16\u8bd1\u5668 cc \u548c\u94fe\u63a5\u7f16\u8f91\u5668 ld \u7684\u624b\u518c\u9875\u3002\u6b64\u5916\uff0cPostgreSQL \u6e90\u4ee3\u7801\u5728 contrib \u76ee\u5f55\u4e2d\u5305\u542b\u82e5\u5e72\u53ef\u7528\u7684\u793a\u4f8b\u3002\u4e0d\u8fc7\uff0c\u5982\u679c\u4f60\u4f9d\u8d56\u8fd9\u4e9b\u793a\u4f8b\uff0c\u5c31\u4f1a\u4f7f\u4f60\u7684\u6a21\u5757\u4f9d\u8d56\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u662f\u5426\u53ef\u7528\u3002

\n

\u521b\u5efa\u5171\u4eab\u5e93\u901a\u5e38\u7c7b\u4f3c\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\uff1a\u5148\u5c06\u6e90\u6587\u4ef6\u7f16\u8bd1\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u518d\u5c06\u76ee\u6807\u6587\u4ef6\u94fe\u63a5\u8d77\u6765\u3002\u76ee\u6807\u6587\u4ef6\u9700\u8981\u7f16\u8bd1\u4e3a\u4f4d\u7f6e\u65e0\u5173\u4ee3\u7801\uff08PIC\uff09\uff0c\u4e5f\u5c31\u662f\u5728\u6982\u5ff5\u4e0a\u5141\u8bb8\u53ef\u6267\u884c\u6587\u4ef6\u52a0\u8f7d\u5b83\u4eec\u65f6\u5c06\u5176\u653e\u5728\u5185\u5b58\u4e2d\u7684\u4efb\u610f\u4f4d\u7f6e\u3002\uff08\u7528\u4e8e\u53ef\u6267\u884c\u6587\u4ef6\u7684\u76ee\u6807\u6587\u4ef6\u901a\u5e38\u4e0d\u8fd9\u6837\u7f16\u8bd1\u3002\uff09\u94fe\u63a5\u5171\u4eab\u5e93\u7684\u547d\u4ee4\u5305\u542b\u7279\u6b8a\u6807\u5fd7\uff0c\u7528\u6765\u533a\u522b\u4e8e\u94fe\u63a5\u53ef\u6267\u884c\u6587\u4ef6\u7684\u547d\u4ee4\u2014\u2014\u81f3\u5c11\u7406\u8bba\u4e0a\u5982\u6b64\uff0c\u67d0\u4e9b\u7cfb\u7edf\u7684\u5b9e\u9645\u505a\u6cd5\u8981\u590d\u6742\u5f97\u591a\u3002

\n

\u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5047\u5b9a\u4f60\u7684\u6e90\u4ee3\u7801\u4f4d\u4e8e\u6587\u4ef6 foo.c \u4e2d\uff0c\u5e76\u5c06\u521b\u5efa\u5171\u4eab\u5e93 foo.so\u3002\u9664\u975e\u53e6\u6709\u8bf4\u660e\uff0c\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u4e3a foo.o\u3002\u5171\u4eab\u5e93\u53ef\u4ee5\u5305\u542b\u591a\u4e2a\u76ee\u6807\u6587\u4ef6\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u53ea\u4f7f\u7528\u4e00\u4e2a\u3002

\n
\n
\n
FreeBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u65f6\u4f7f\u7528\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n

\u8fd9\u4ece FreeBSD 13.0 \u8d77\u9002\u7528\uff1b\u66f4\u65e9\u7248\u672c\u4f7f\u7528\u7684\u662f gcc \u7f16\u8bd1\u5668\u3002

\n
\n
Linux
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u521b\u5efa\u5171\u4eab\u5e93\u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -shared\u3002\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
cc -fPIC -c foo.c\ncc -shared -o foo.so foo.o\n
\n
\n
macOS
\n
\n

\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\u3002\u5b83\u5047\u5b9a\u5f00\u53d1\u8005\u5de5\u5177\u5df2\u7ecf\u5b89\u88c5\u3002

\n
cc -c foo.c\ncc -bundle -flat_namespace -undefined suppress -o foo.so foo.o\n
\n
\n
NetBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u5bf9\u4e8e ELF \u7cfb\u7edf\uff0c\u4f7f\u7528\u5e26\u6709 -shared \u9009\u9879\u7684\u7f16\u8bd1\u5668\u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002\u5bf9\u4e8e\u8f83\u65e9\u7684\u975e ELF \u7cfb\u7edf\uff0c\u5219\u4f7f\u7528 ld -Bshareable\u3002

\n
gcc -fPIC -c foo.c\ngcc -shared -o foo.so foo.o\n
\n
\n
OpenBSD
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\u662f -fPIC\u3002\u4f7f\u7528 ld -Bshareable \u6765\u94fe\u63a5\u5171\u4eab\u5e93\u3002

\n
gcc -fPIC -c foo.c\nld -Bshareable -o foo.so foo.o\n
\n
\n
Solaris
\n
\n

\u751f\u6210 PIC \u7684\u7f16\u8bd1\u5668\u9009\u9879\uff0c\u5bf9\u4e8e Sun \u7f16\u8bd1\u5668\u662f -KPIC\uff0c\u800c -fPIC \u5219\u7528\u4e8e GCC\u3002\u94fe\u63a5\u5171\u4eab\u5e93\u65f6\uff0c\u4e24\u79cd\u7f16\u8bd1\u5668\u90fd\u53ef\u4ee5\u4f7f\u7528 -G\uff0c\u6216\u8005\u4e5f\u53ef\u4ee5\u6539\u7528 -shared\uff0c\u4f46\u8fd9\u53ea\u9002\u7528\u4e8e GCC\u3002

\n
cc -KPIC -c foo.c\ncc -G -o foo.so foo.o\n
\n

\u6216\u8005

\n
gcc -fPIC -c foo.c\ngcc -G -o foo.so foo.o\n
\n
\n
\n
\n
\n

\u63d0\u793a

\n

\u5982\u679c\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4f60\u6765\u8bf4\u8fc7\u4e8e\u590d\u6742\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528 GNU Libtool\uff0c\u5b83\u901a\u8fc7\u7edf\u4e00\u63a5\u53e3\u9690\u85cf\u4e86\u5e73\u53f0\u5dee\u5f02\u3002

\n
\n

\u751f\u6210\u7684\u5171\u4eab\u5e93\u6587\u4ef6\u968f\u540e\u5c31\u53ef\u4ee5\u88c5\u8f7d\u5230 PostgreSQL \u4e2d\u3002\u5728\u5411 CREATE FUNCTION \u547d\u4ee4\u6307\u5b9a\u6587\u4ef6\u540d\u65f6\uff0c\u5fc5\u987b\u7ed9\u51fa\u5171\u4eab\u5e93\u6587\u4ef6\u540d\uff0c\u800c\u4e0d\u662f\u4e2d\u95f4\u76ee\u6807\u6587\u4ef6\u540d\u3002\u8bf7\u6ce8\u610f\uff0c\u7cfb\u7edf\u6807\u51c6\u7684\u5171\u4eab\u5e93\u6269\u5c55\u540d\uff08\u901a\u5e38\u662f .so \u6216 .sl\uff09\u53ef\u4ee5\u5728 CREATE FUNCTION \u547d\u4ee4\u4e2d\u7701\u7565\uff0c\u5e76\u4e14\u901a\u5e38\u4e5f\u5e94\u7701\u7565\uff0c\u4ee5\u83b7\u5f97\u6700\u4f73\u53ef\u79fb\u690d\u6027\u3002

\n

\u5173\u4e8e\u670d\u52a1\u5668\u671f\u671b\u5728\u4f55\u5904\u627e\u5230\u5171\u4eab\u5e93\u6587\u4ef6\uff0c\u8bf7\u56de\u5934\u53c2\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\u3002

\n
\n
\n
\n
\n
\n

36.10.6. \u670d\u52a1\u5668 API \u548c ABI \u7a33\u5b9a\u6027\u6307\u5357

\n
\n
\n
\n

\u672c\u8282\u5411\u6269\u5c55\u548c\u5176\u4ed6\u670d\u52a1\u5668\u63d2\u4ef6\u7684\u4f5c\u8005\u63d0\u4f9b\u6709\u5173 PostgreSQL \u670d\u52a1\u5668 API \u4e0e ABI \u7a33\u5b9a\u6027\u7684\u6307\u5bfc\u3002

\n
\n
\n
\n
\n

\n
\n
\n

36.10.6.1.\u00a0\u6982\u8ff0

\n
\n
\n

\n
\n
\n
\n

PostgreSQL \u670d\u52a1\u5668\u4e3a\u63d2\u4ef6\u63d0\u4f9b\u4e86\u591a\u4e2a\u8fb9\u754c\u6e05\u6670\u7684 API\uff0c\u4f8b\u5982\u672c\u7ae0\u4ecb\u7ecd\u7684\u51fd\u6570\u7ba1\u7406\u5668 fmgr\u3001SPI\uff08\u7b2c 45 \u7ae0\uff09\u4ee5\u53ca\u4e13\u4e3a\u6269\u5c55\u8bbe\u8ba1\u7684\u5404\u79cd\u94a9\u5b50\u3002\u8fd9\u4e9b\u63a5\u53e3\u7ecf\u8fc7\u8c28\u614e\u7ef4\u62a4\uff0c\u4ee5\u4fdd\u6301\u957f\u671f\u7a33\u5b9a\u6027\u548c\u517c\u5bb9\u6027\u3002\u4e0d\u8fc7\uff0c\u670d\u52a1\u5668\u4e2d\u5168\u90e8\u5168\u5c40\u51fd\u6570\u548c\u53d8\u91cf\u5b9e\u9645\u4e0a\u90fd\u6784\u6210\u4e86\u53ef\u516c\u5f00\u4f7f\u7528\u7684 API\uff0c\u5176\u4e2d\u5927\u90e8\u5206\u5728\u8bbe\u8ba1\u65f6\u5e76\u672a\u8003\u8651\u53ef\u6269\u5c55\u6027\u548c\u957f\u671f\u7a33\u5b9a\u6027\u3002

\n

\u56e0\u6b64\uff0c\u867d\u7136\u4f7f\u7528\u8fd9\u4e9b\u63a5\u53e3\u662f\u5b8c\u5168\u5141\u8bb8\u7684\uff0c\u4f46\u8d8a\u662f\u504f\u79bb\u90a3\u4e9b\u4e45\u7ecf\u5b9e\u8df5\u8003\u9a8c\u7684\u8def\u5f84\uff0c\u5c06\u6765\u9047\u5230 API \u6216 ABI \u517c\u5bb9\u6027\u95ee\u9898\u7684\u53ef\u80fd\u6027\u5c31\u8d8a\u5927\u3002\u9f13\u52b1\u6269\u5c55\u4f5c\u8005\u53cd\u9988\u81ea\u5df1\u7684\u9700\u6c42\uff0c\u4ee5\u4fbf\u968f\u7740\u65f6\u95f4\u63a8\u79fb\u548c\u65b0\u7528\u6cd5\u7684\u51fa\u73b0\uff0c\u67d0\u4e9b\u63a5\u53e3\u80fd\u591f\u88ab\u89c6\u4e3a\u66f4\u7a33\u5b9a\uff0c\u6216\u8005\u53ef\u4ee5\u52a0\u5165\u65b0\u7684\u3001\u8bbe\u8ba1\u66f4\u5b8c\u5584\u7684\u63a5\u53e3\u3002

\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.6.2.\u00a0API \u517c\u5bb9\u6027

\n
\n
\n

\n
\n
\n
\n

API\uff0c\u5373\u5e94\u7528\u7a0b\u5e8f\u7f16\u7a0b\u63a5\u53e3\uff0c\u662f\u7f16\u8bd1\u65f6\u4f7f\u7528\u7684\u63a5\u53e3\u3002

\n
\n
\n
\n
\n
36.10.6.2.1.\u00a0Major Versions
\n
\n
\n
\n

\u5728 PostgreSQL \u4e0d\u540c\u4e3b\u7248\u672c\u4e4b\u95f4\uff0c\u4e0d\u627f\u8bfa API \u517c\u5bb9\u6027\u3002\u56e0\u6b64\uff0c\u6269\u5c55\u4ee3\u7801\u53ef\u80fd\u9700\u8981\u4fee\u6539\u6e90\u4ee3\u7801\u624d\u80fd\u540c\u65f6\u652f\u6301\u591a\u4e2a\u4e3b\u7248\u672c\u3002\u8fd9\u7c7b\u5dee\u5f02\u901a\u5e38\u53ef\u4ee5\u901a\u8fc7\u9884\u5904\u7406\u5668\u6761\u4ef6\uff08\u4f8b\u5982 #if PG_VERSION_NUM >= 160000\uff09\u6765\u7ba1\u7406\u3002\u90a3\u4e9b\u4f7f\u7528\u4e86\u8fb9\u754c\u6e05\u6670\u63a5\u53e3\u4e4b\u5916\u80fd\u529b\u7684\u590d\u6742\u6269\u5c55\uff0c\u901a\u5e38\u6bcf\u4e2a\u670d\u52a1\u5668\u4e3b\u7248\u672c\u90fd\u9700\u8981\u505a\u5c11\u91cf\u8fd9\u7c7b\u4fee\u6539\u3002

\n
\n
\n
\n
\n
\n
36.10.6.2.2.\u00a0Minor Versions
\n
\n
\n
\n

PostgreSQL \u4f1a\u5c3d\u529b\u907f\u514d\u5728\u5c0f\u7248\u672c\u53d1\u5e03\u4e2d\u7834\u574f\u670d\u52a1\u5668 API\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u80fd\u9488\u5bf9\u67d0\u4e2a\u5c0f\u7248\u672c\u7f16\u8bd1\u5e76\u6b63\u5e38\u5de5\u4f5c\u7684\u6269\u5c55\u4ee3\u7801\uff0c\u4e5f\u5e94\u5f53\u80fd\u591f\u9488\u5bf9\u540c\u4e00\u4e3b\u7248\u672c\u7684\u5176\u4ed6\u4efb\u610f\u5c0f\u7248\u672c\uff08\u65e0\u8bba\u8fc7\u53bb\u8fd8\u662f\u5c06\u6765\uff09\u7f16\u8bd1\u5e76\u6b63\u5e38\u5de5\u4f5c\u3002

\n

\u5982\u679c\u786e\u5b9e\u9700\u8981\u505a\u51fa\u53d8\u66f4\uff0c\u4e5f\u4f1a\u5728\u8003\u8651\u6269\u5c55\u9700\u6c42\u7684\u524d\u63d0\u4e0b\u8c28\u614e\u7ba1\u7406\u3002\u8fd9\u7c7b\u53d8\u66f4\u4f1a\u5728\u53d1\u5e03\u8bf4\u660e\uff08\u9644\u5f55\u00a0E\uff09\u4e2d\u8fdb\u884c\u8bf4\u660e\u3002

\n
\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.6.3.\u00a0ABI \u517c\u5bb9\u6027

\n
\n
\n

\n
\n
\n
\n

ABI\uff0c\u5373\u5e94\u7528\u7a0b\u5e8f\u4e8c\u8fdb\u5236\u63a5\u53e3\uff0c\u662f\u8fd0\u884c\u65f6\u4f7f\u7528\u7684\u63a5\u53e3\u3002

\n
\n
\n
\n
\n
36.10.6.3.1.\u00a0Major Versions
\n
\n
\n
\n

\u4e0d\u540c\u4e3b\u7248\u672c\u7684\u670d\u52a1\u5668\u5728 ABI \u4e0a\u662f\u6709\u610f\u4e0d\u517c\u5bb9\u7684\u3002\u56e0\u6b64\uff0c\u4f7f\u7528\u670d\u52a1\u5668 API \u7684\u6269\u5c55\u5fc5\u987b\u9488\u5bf9\u6bcf\u4e00\u4e2a\u4e3b\u7248\u672c\u91cd\u65b0\u7f16\u8bd1\u3002\u5305\u542b PG_MODULE_MAGIC\uff08\u89c1\u7b2c\u00a036.10.1\u00a0\u8282\uff09\u53ef\u4ee5\u786e\u4fdd\u9488\u5bf9\u67d0\u4e2a\u4e3b\u7248\u672c\u7f16\u8bd1\u7684\u4ee3\u7801\u4f1a\u88ab\u5176\u4ed6\u4e3b\u7248\u672c\u62d2\u7edd\u3002

\n
\n
\n
\n
\n
\n
36.10.6.3.2.\u00a0Minor Versions
\n
\n
\n
\n

PostgreSQL \u4f1a\u5c3d\u529b\u907f\u514d\u5728\u5c0f\u7248\u672c\u53d1\u5e03\u4e2d\u7834\u574f\u670d\u52a1\u5668 ABI\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u9488\u5bf9\u4efb\u610f\u4e00\u4e2a\u5c0f\u7248\u672c\u7f16\u8bd1\u7684\u6269\u5c55\uff0c\u5e94\u5f53\u80fd\u4e0e\u540c\u4e00\u4e3b\u7248\u672c\u8fc7\u53bb\u6216\u5c06\u6765\u7684\u5176\u4ed6\u4efb\u610f\u5c0f\u7248\u672c\u4e00\u8d77\u5de5\u4f5c\u3002

\n

\u5982\u679c\u786e\u5b9e\u9700\u8981\u53d8\u66f4\uff0cPostgreSQL \u4f1a\u5c3d\u91cf\u9009\u62e9\u4fb5\u5165\u6027\u6700\u5c0f\u7684\u65b9\u5f0f\uff0c\u4f8b\u5982\u628a\u65b0\u5b57\u6bb5\u585e\u8fdb\u586b\u5145\u7a7a\u95f4\uff0c\u6216\u8005\u9644\u52a0\u5230\u7ed3\u6784\u4f53\u672b\u5c3e\u3002\u8fd9\u7c7b\u4fee\u6539\u901a\u5e38\u4e0d\u5e94\u5f71\u54cd\u6269\u5c55\uff0c\u9664\u975e\u6269\u5c55\u4f7f\u7528\u4e86\u975e\u5e38\u4e0d\u5bfb\u5e38\u7684\u4ee3\u7801\u6a21\u5f0f\u3002

\n

\u7136\u800c\uff0c\u5728\u6781\u5c11\u6570\u60c5\u51b5\u4e0b\uff0c\u5373\u4f7f\u662f\u8fd9\u79cd\u975e\u4fb5\u5165\u5f0f\u53d8\u66f4\u4e5f\u53ef\u80fd\u4e0d\u73b0\u5b9e\u751a\u81f3\u4e0d\u53ef\u80fd\u505a\u5230\u3002\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\u65f6\uff0c\u4e5f\u4f1a\u5728\u8003\u8651\u6269\u5c55\u9700\u6c42\u7684\u524d\u63d0\u4e0b\u8c28\u614e\u7ba1\u7406\u8be5\u53d8\u66f4\u3002\u8fd9\u7c7b\u53d8\u66f4\u540c\u6837\u4f1a\u8bb0\u5f55\u5728\u53d1\u5e03\u8bf4\u660e\uff08\u9644\u5f55\u00a0E\uff09\u4e2d\u3002

\n

\u4f46\u8bf7\u6ce8\u610f\uff0c\u670d\u52a1\u5668\u4e2d\u6709\u5f88\u591a\u90e8\u5206\u5e76\u4e0d\u662f\u4f5c\u4e3a\u53ef\u516c\u5f00\u4f7f\u7528\u7684 API \u6765\u8bbe\u8ba1\u548c\u7ef4\u62a4\u7684\uff08\u800c\u4e14\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u5176\u771f\u5b9e\u8fb9\u754c\u4e5f\u5e76\u4e0d\u6e05\u6670\uff09\u3002\u5982\u679c\u51fa\u73b0\u7d27\u6025\u9700\u6c42\uff0c\u5bf9\u8fd9\u4e9b\u90e8\u5206\u8fdb\u884c\u4fee\u6539\u65f6\uff0c\u81ea\u7136\u4f1a\u6bd4\u4fee\u6539\u90a3\u4e9b\u8fb9\u754c\u6e05\u695a\u4e14\u5e7f\u6cdb\u4f7f\u7528\u7684\u63a5\u53e3\u65f6\u66f4\u5c11\u8003\u8651\u6269\u5c55\u4ee3\u7801\u7684\u517c\u5bb9\u6027\u3002

\n

\u6b64\u5916\uff0c\u5728\u7f3a\u4e4f\u81ea\u52a8\u5316\u68c0\u6d4b\u8fd9\u7c7b\u53d8\u5316\u7684\u673a\u5236\u65f6\uff0c\u8fd9\u5e76\u4e0d\u80fd\u6784\u6210\u4e25\u683c\u4fdd\u8bc1\uff1b\u4e0d\u8fc7\u4ece\u5386\u53f2\u4e0a\u770b\uff0c\u8fd9\u79cd\u7834\u574f\u6027\u53d8\u5316\u6781\u4e3a\u7f55\u89c1\u3002

\n
\n
\n
\n
\n
\n
\n
\n

36.10.7. \u590d\u5408\u7c7b\u578b\u53c2\u6570

\n
\n
\n
\n

\u590d\u5408\u7c7b\u578b\u6ca1\u6709\u50cf C \u7ed3\u6784\u4f53\u90a3\u6837\u7684\u56fa\u5b9a\u5e03\u5c40\u3002\u590d\u5408\u7c7b\u578b\u7684\u5b9e\u4f8b\u53ef\u80fd\u5305\u542b\u7a7a\u503c\u5b57\u6bb5\u3002\u6b64\u5916\uff0c\u7ee7\u627f\u5c42\u6b21\u4e2d\u7684\u590d\u5408\u7c7b\u578b\u53ef\u80fd\u5177\u6709\u548c\u540c\u4e00\u7ee7\u627f\u5c42\u6b21\u4e2d\u5176\u4ed6\u6210\u5458\u4e0d\u540c\u7684\u5b57\u6bb5\u3002\u56e0\u6b64\uff0cPostgreSQL\u63d0\u4f9b\u4e86\u51fd\u6570\u63a5\u53e3\u4ee5\u4fbf\u4ece C \u8bbf\u95ee\u590d\u5408\u7c7b\u578b\u7684\u5b57\u6bb5\u3002

\n

\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u51fd\u6570\u6765\u56de\u7b54\u67e5\u8be2\uff1a

\n
SELECT name, c_overpaid(emp, 1500) AS overpaid\n    FROM emp\n    WHERE name = 'Bill' OR name = 'Sam';\n
\n

\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff0c\u53ef\u4ee5\u5c06 c_overpaid \u5b9a\u4e49\u4e3a\uff1a

\n
#include \"postgres.h\"\n#include \"executor/executor.h\"  /* for GetAttributeByName() */\n\nPG_MODULE_MAGIC;\n\nPG_FUNCTION_INFO_V1(c_overpaid);\n\nDatum\nc_overpaid(PG_FUNCTION_ARGS)\n{\n    HeapTupleHeader  t = PG_GETARG_HEAPTUPLEHEADER(0);\n    int32            limit = PG_GETARG_INT32(1);\n    bool isnull;\n    Datum salary;\n\n    salary = GetAttributeByName(t, \"salary\", &isnull);\n    if (isnull)\n        PG_RETURN_BOOL(false);\n    /* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary. */\n\n    PG_RETURN_BOOL(DatumGetInt32(salary) > limit);\n}\n\n
\n

GetAttributeByName \u662f PostgreSQL \u7684\u4e00\u4e2a\u7cfb\u7edf\u51fd\u6570\uff0c\u7528\u4e8e\u4ece\u6307\u5b9a\u884c\u4e2d\u53d6\u51fa\u5c5e\u6027\u3002\u5b83\u6709\u4e09\u4e2a\u53c2\u6570\uff1a\u4f20\u5165\u51fd\u6570\u7684 HeapTupleHeader \u7c7b\u578b\u53c2\u6570\u3001\u6240\u9700\u5c5e\u6027\u7684\u540d\u79f0\uff0c\u4ee5\u53ca\u4e00\u4e2a\u7528\u4e8e\u6307\u793a\u8be5\u5c5e\u6027\u662f\u5426\u4e3a null \u7684\u8fd4\u56de\u53c2\u6570\u3002GetAttributeByName \u8fd4\u56de\u4e00\u4e2a Datum \u503c\uff0c\u4f60\u53ef\u4ee5\u7528\u9002\u5f53\u7684 DatumGetXXX() \u51fd\u6570\u628a\u5b83\u8f6c\u6362\u4e3a\u6b63\u786e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6ce8\u610f\uff0c\u5982\u679c null \u6807\u5fd7\u88ab\u8bbe\u7f6e\uff0c\u90a3\u4e48\u8fd4\u56de\u503c\u672c\u8eab\u6ca1\u6709\u610f\u4e49\uff1b\u5728\u5c1d\u8bd5\u5bf9\u7ed3\u679c\u505a\u4efb\u4f55\u5904\u7406\u4e4b\u524d\uff0c\u52a1\u5fc5\u5148\u68c0\u67e5\u8fd9\u4e2a null \u6807\u5fd7\u3002

\n

\u4e5f\u6709GetAttributeByNum\u51fd\u6570\uff0c\u5b83\u53ef\u4ee5\u7528\u76ee\u6807\u5c5e\u6027\u7684\u5217\u53f7\u800c\u4e0d\u662f\u5c5e\u6027\u540d\u6765\u9009\u62e9\u76ee\u6807\u5c5e\u6027\u3002

\n

\u4e0b\u9762\u7684\u547d\u4ee4\u58f0\u660e SQL \u4e2d\u7684c_overpaid\uff1a

\n
CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean\n    AS 'DIRECTORY/funcs', 'c_overpaid'\n    LANGUAGE C STRICT;\n
\n

\u6ce8\u610f\u6211\u4eec\u7528\u4e86STRICT\uff0c\u8fd9\u6837\u6211\u4eec\u4e0d\u9700\u8981\u68c0\u67e5\u8f93\u5165\u53c2\u6570\u662f\u5426\u4e3a NULL\u3002

\n
\n
\n
\n
\n
\n

36.10.8. \u8fd4\u56de\u884c\uff08\u590d\u5408\u7c7b\u578b\uff09

\n
\n
\n
\n

\u8981\u4ece C \u8bed\u8a00\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u884c\u6216\u4e00\u4e2a\u590d\u5408\u7c7b\u578b\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u5957\u7279\u6b8a\u7684 API\uff0c\u5b83\u901a\u8fc7\u4e00\u7ec4\u5b8f\u548c\u51fd\u6570\u9690\u85cf\u4e86\u6784\u9020\u590d\u5408\u6570\u636e\u7c7b\u578b\u65f6\u7684\u5927\u90e8\u5206\u590d\u6742\u6027\u3002\u8981\u4f7f\u7528\u8fd9\u5957 API\uff0c\u6e90\u6587\u4ef6\u4e2d\u5fc5\u987b\u5305\u542b\uff1a

\n
#include \"funcapi.h\"\n
\n

\u6784\u9020\u590d\u5408\u6570\u636e\u503c\uff08\u4e0b\u6587\u7b80\u79f0\u201c\u5143\u7ec4\u201d\uff09\u6709\u4e24\u79cd\u65b9\u5f0f\uff1a\u4e00\u79cd\u662f\u4ece Datum \u503c\u6570\u7ec4\u6784\u9020\uff0c\u53e6\u4e00\u79cd\u662f\u4ece C \u5b57\u7b26\u4e32\u6570\u7ec4\u6784\u9020\uff0c\u8fd9\u4e9b\u5b57\u7b26\u4e32\u4f1a\u4f20\u7ed9\u8be5\u5143\u7ec4\u5404\u5217\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u8f6c\u6362\u51fd\u6570\u3002\u65e0\u8bba\u91c7\u7528\u54ea\u79cd\u65b9\u5f0f\uff0c\u9996\u5148\u90fd\u9700\u8981\u83b7\u53d6\u6216\u6784\u9020\u63cf\u8ff0\u8be5\u5143\u7ec4\u7ed3\u6784\u7684 TupleDesc\u3002\u5904\u7406 Datum \u65f6\uff0c\u9700\u8981\u628a TupleDesc \u4f20\u7ed9 BlessTupleDesc\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 heap_form_tuple\u3002\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u5219\u8981\u628a TupleDesc \u4f20\u7ed9 TupleDescGetAttInMetadata\uff0c\u7136\u540e\u4e3a\u6bcf\u4e00\u884c\u8c03\u7528 BuildTupleFromCStrings\u3002\u5bf9\u4e8e\u8fd4\u56de\u5143\u7ec4\u96c6\u5408\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51c6\u5907\u6b65\u9aa4\u53ef\u4ee5\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u51fd\u6570\u65f6\u4e00\u6b21\u6027\u5b8c\u6210\u3002

\n

\u6709\u4e00\u4e9b\u8f85\u52a9\u51fd\u6570\u53ef\u4ee5\u7528\u6765\u8bbe\u7f6e\u6240\u9700\u7684 TupleDesc\u3002\u5728\u5927\u591a\u6570\u8fd4\u56de\u590d\u5408\u503c\u7684\u51fd\u6570\u4e2d\uff0c\u63a8\u8350\u7684\u505a\u6cd5\u662f\u8c03\u7528\uff1a

\n
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,\n                                   Oid *resultTypeId,\n                                   TupleDesc *resultTupleDesc)\n
\n

\u4f20\u5165\u8c03\u7528\u51fd\u6570\u672c\u8eab\u6536\u5230\u7684\u540c\u4e00\u4e2a fcinfo \u7ed3\u6784\u4f53\uff08\u8fd9\u5f53\u7136\u8981\u6c42\u4f7f\u7528\u7248\u672c 1 \u8c03\u7528\u7ea6\u5b9a\uff09\u3002resultTypeId \u53ef\u4ee5\u6307\u5b9a\u4e3a NULL\uff0c\u4e5f\u53ef\u4ee5\u6307\u5b9a\u4e3a\u4e00\u4e2a\u672c\u5730\u53d8\u91cf\u7684\u5730\u5740\uff0c\u7528\u4e8e\u63a5\u6536\u51fd\u6570\u7ed3\u679c\u7c7b\u578b\u7684 OID\u3002resultTupleDesc \u5e94\u5f53\u662f\u4e00\u4e2a\u672c\u5730 TupleDesc \u53d8\u91cf\u7684\u5730\u5740\u3002\u68c0\u67e5\u8fd4\u56de\u7ed3\u679c\u662f\u5426\u4e3a TYPEFUNC_COMPOSITE\uff1b\u5982\u679c\u662f\uff0cresultTupleDesc \u5c31\u4f1a\u88ab\u586b\u5165\u6240\u9700\u7684 TupleDesc\u3002\uff08\u5982\u679c\u4e0d\u662f\uff0c\u53ef\u4ee5\u62a5\u544a\u4e00\u4e2a\u7c7b\u4f3c\u201cfunction returning record called in context that cannot accept type record\u201d\u7684\u9519\u8bef\u3002\uff09

\n
\n

\u63d0\u793a

\n

get_call_result_type\u80fd\u591f\u89e3\u6790\u4e00\u4e2a\u591a\u6001\u51fd\u6570\u7ed3\u679c\u7684\u5b9e\u9645\u7c7b\u578b\uff0c\u56e0\u6b64\u4e0d\u4ec5\u5728\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u51fd\u6570\u4e2d\uff0c\u5728\u8fd4\u56de\u6807\u91cf\u591a\u6001\u7ed3\u679c\u7684\u51fd\u6570\u4e2d\u5b83\u4e5f\u662f\u975e\u5e38\u6709\u7528\u7684\u3002resultTypeId\u8f93\u51fa\u4e3b\u8981\u7528\u4e8e\u8fd4\u56de\u591a\u6001\u6807\u91cf\u7684\u51fd\u6570\u3002

\n
\n
\n

\u6ce8\u610f

\n

get_call_result_type\u6709\u4e00\u4e2a\u5144\u5f1f get_expr_result_type\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u88ab\u8868\u793a\u4e3a\u4e00\u68f5\u8868\u8fbe\u5f0f\u6811\u7684\u51fd\u6570\u8c03\u7528\u7684\u8f93\u51fa\u7c7b\u578b\u3002\u5728\u5c1d\u8bd5\u4ece\u51fd\u6570\u81ea\u8eab\u5916\u90e8\u786e\u5b9a\u7ed3\u679c\u7c7b\u578b\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e5f\u6709\u4e00\u4e2aget_func_result_type\uff0c\u5f53\u53ea\u6709\u51fd\u6570\u7684 OID \u53ef\u7528\u65f6\u53ef\u4ee5\u7528\u5b83\u3002\u4e0d\u8fc7\u8fd9\u4e9b\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u88ab\u58f0\u660e\u4e3a\u8fd4\u56derecord\u7684\u51fd\u6570\uff0c\u5e76\u4e14get_func_result_type\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\uff0c\u56e0\u6b64\u4f60\u5e94\u8be5\u4f18\u5148\u4f7f\u7528get_call_result_type\u3002

\n
\n

\u66f4\u65e9\u3001\u73b0\u5728\u5df2\u88ab\u5f03\u7528\u7684\u83b7\u53d6TupleDesc\u7684\u51fd\u6570\u6709\uff1a

\n
TupleDesc RelationNameGetTupleDesc(const char *relname)\n
\n

\u5b83\u53ef\u4ee5\u4e3a\u4e00\u4e2a\u6307\u5b9a\u540d\u79f0\u7684\u5173\u7cfb\u7684\u884c\u7c7b\u578b\u5f97\u5230TupleDesc\uff0c\u8fd8\u6709\uff1a

\n
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)\n
\n

\u53ef\u4ee5\u57fa\u4e8e\u4e00\u4e2a\u7c7b\u578b OID \u5f97\u5230TupleDesc\u3002\u8fd9\u53ef\u4ee5\u88ab\u7528\u6765\u4e3a\u4e00\u79cd\u57fa\u672c\u6216\u8005\u590d\u5408\u7c7b\u578b\u83b7\u5f97TupleDesc\u3002\u4e0d\u8fc7\uff0c\u5bf9\u4e8e\u8fd4\u56derecord\u7684\u51fd\u6570\u5b83\u4e0d\u8d77\u4f5c\u7528\uff0c\u5e76\u4e14\u5b83\u65e0\u6cd5\u89e3\u6790\u591a\u6001\u7c7b\u578b\u3002

\n

\u4e00\u65e6\u6709\u4e86\u4e00\u4e2aTupleDesc\uff0c\u5982\u679c\u8ba1\u5212\u5904\u7406 Datum\uff0c\u53ef\u4ee5\u8c03\u7528\uff1a

\n
TupleDesc BlessTupleDesc(TupleDesc tupdesc)\n
\n

\u5982\u679c\u8ba1\u5212\u5904\u7406 C \u5b57\u7b26\u4e32\uff0c\u53ef\u8c03\u7528\uff1a

\n
AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)\n
\n

\u5982\u679c\u6b63\u5728\u7f16\u5199\u4e00\u4e2a\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u628a\u8fd9\u4e9b\u51fd\u6570\u7684\u7ed3\u679c\u4fdd\u5b58\u5728 FuncCallContext\u7ed3\u6784\u4f53\u4e2d \u2014 \u5206\u522b\u4f7f\u7528 tuple_desc\u6216\u8005attinmeta\u5b57\u6bb5\u3002

\n

\u5728\u5904\u7406 Datum \u65f6\uff0c\u4f7f\u7528

\n
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)\n
\n

\u6765\u7528 Datum \u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002

\n

\u5728\u5904\u7406 C \u5b57\u7b26\u4e32\u65f6\uff0c\u4f7f\u7528

\n
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)\n
\n

\u6765\u7528 C \u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u7528\u6237\u6570\u636e\u6784\u5efa\u4e00\u4e2aHeapTuple\u3002values\u662f\u4e00\u4e2a C \u5b57\u7b26\u4e32\u6570\u7ec4\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u8fd4\u56de\u884c\u7684\u4e00\u4e2a\u5c5e\u6027\u3002\u6bcf\u4e00\u4e2a C \u5b57\u7b26\u4e32\u5e94\u8be5\u662f\u8be5\u5c5e\u6027\u6570\u636e\u7c7b\u578b\u7684\u8f93\u5165\u51fd\u6570\u6240\u671f\u671b\u7684\u683c\u5f0f\u3002\u4e3a\u4e86\u5bf9\u4e00\u4e2a\u5c5e\u6027\u8fd4\u56de\u7a7a\u503c\uff0cvalues\u6570\u7ec4\u4e2d\u5bf9\u5e94\u7684\u6307\u9488\u5e94\u8be5\u88ab\u8bbe\u7f6e\u4e3aNULL\u3002\u5bf9\u4e8e\u4f60\u8fd4\u56de\u7684\u6bcf\u4e00\u884c\u90fd\u9700\u8981\u518d\u6b21\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u3002

\n

\u4e00\u65e6\u5df2\u7ecf\u6784\u5efa\u4e86\u4e00\u4e2a\u8981\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u7684\u5143\u7ec4\uff0c\u5b83\u5fc5\u987b\u88ab\u8f6c\u6362\u6210\u4e00\u4e2a Datum\u3002\u4f7f\u7528

\n
HeapTupleGetDatum(HeapTuple tuple)\n
\n

\u53ef\u628a\u4e00\u4e2aHeapTuple\u8f6c\u6362\u6210\u5408\u6cd5\u7684 Datum\u3002\u5982\u679c\u4f60\u53ea\u60f3\u8fd4\u56de\u4e00\u884c\uff0c\u90a3\u4e48\u8fd9\u4e2aDatum\u53ef\u4ee5\u88ab\u76f4\u63a5\u8fd4\u56de\uff0c\u5728\u4e00\u4e2a\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u4e2d\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5f53\u505a\u5f53\u524d\u7684\u8fd4\u56de\u503c\u3002

\n

\u4e0b\u4e00\u8282\u4e2d\u4f1a\u6709\u4e00\u4e2a\u793a\u4f8b\u3002

\n
\n
\n
\n
\n
\n

36.10.9. \u8fd4\u56de\u96c6\u5408

\n
\n
\n
\n

C \u8bed\u8a00\u51fd\u6570\u6709\u4e24\u79cd\u8fd4\u56de\u96c6\u5408\uff08\u591a\u884c\uff09\u7684\u65b9\u6cd5\u3002\u7b2c\u4e00\u79cd\u79f0\u4e3a ValuePerCall \u6a21\u5f0f\uff1a\u53cd\u590d\u8c03\u7528\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff0c\u6bcf\u6b21\u4f20\u5165\u76f8\u540c\u53c2\u6570\uff0c\u6bcf\u6b21\u8fd4\u56de\u4e00\u884c\u65b0\u6570\u636e\uff0c\u76f4\u5230\u6ca1\u6709\u66f4\u591a\u884c\uff0c\u5e76\u4ee5\u8fd4\u56de NULL \u8868\u793a\u7ed3\u675f\u3002\u56e0\u6b64\uff0c\u8fd4\u56de\u96c6\u5408\u7684\u51fd\u6570\uff08SRF\uff09\u5fc5\u987b\u8de8\u8c03\u7528\u4fdd\u5b58\u8db3\u591f\u7684\u72b6\u6001\uff0c\u8bb0\u5f55\u6267\u884c\u8fdb\u5ea6\uff0c\u786e\u4fdd\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u6b63\u786e\u7684\u4e0b\u4e00\u9879\u3002\u7b2c\u4e8c\u79cd\u79f0\u4e3a Materialize \u6a21\u5f0f\uff1aSRF \u586b\u5145\u5e76\u8fd4\u56de\u4e00\u4e2a\u5305\u542b\u5168\u90e8\u7ed3\u679c\u7684 tuplestore \u5bf9\u8c61\u3002\u6574\u4e2a\u7ed3\u679c\u53ea\u9700\u8c03\u7528\u4e00\u6b21\uff0c\u56e0\u6b64\u65e0\u9700\u4fdd\u5b58\u8c03\u7528\u4e4b\u95f4\u7684\u72b6\u6001\u3002

\n

\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u65f6\uff0c\u91cd\u8981\u7684\u662f\u8981\u8bb0\u4f4f\u67e5\u8be2\u4e0d\u80fd\u4fdd\u8bc1\u8fd0\u884c\u5b8c\u6210\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u7531\u4e8e\u8bf8\u5982LIMIT\u4e4b\u7c7b\u7684\u9009\u9879\uff0c\u6267\u884c\u5668\u53ef\u80fd\u4f1a\u5728\u83b7\u53d6\u6240\u6709\u884c\u4e4b\u524d\u505c\u6b62\u8c03\u7528\u96c6\u5408\u8fd4\u56de\u51fd\u6570\u3002\u8fd9\u610f\u5473\u7740\u5728\u6700\u540e\u4e00\u6b21\u8c03\u7528\u4e2d\u6267\u884c\u6e05\u7406\u6d3b\u52a8\u662f\u4e0d\u5b89\u5168\u7684\uff0c\u56e0\u4e3a\u8fd9\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u53d1\u751f\u3002\u5bf9\u4e8e\u9700\u8981\u8bbf\u95ee\u5916\u90e8\u8d44\u6e90\uff08\u4f8b\u5982\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u7684\u51fd\u6570\uff0c\u5efa\u8bae\u4f7f\u7528 Materialize \u6a21\u5f0f\u3002

\n

\u672c\u8282\u7684\u5176\u4f59\u90e8\u5206\u8bb0\u5f55\u4e86\u4e00\u7ec4\u4f7f\u7528 ValuePerCall \u6a21\u5f0f\u7684 SRF \u5e38\u7528\uff08\u5c3d\u7ba1\u4e0d\u662f\u5fc5\u987b\u4f7f\u7528\uff09\u7684\u8f85\u52a9\u5b8f\u3002\u6709\u5173 Materialize \u6a21\u5f0f\u7684\u5176\u4ed6\u8be6\u7ec6\u4fe1\u606f\u53ef\u4ee5\u5728src/backend/utils/fmgr/README\u4e2d\u627e\u5230\u3002\u6b64\u5916\uff0cPostgreSQL\u6e90\u4ee3\u7801\u5206\u53d1\u4e2d\u7684contrib \u6a21\u5757\u5305\u542b\u8bb8\u591a\u4f7f\u7528 ValuePerCall \u548c Materialize \u6a21\u5f0f\u7684 SRF \u793a\u4f8b\u3002

\n

\u8981\u4f7f\u7528\u6b64\u5904\u63cf\u8ff0\u7684 ValuePerCall \u652f\u6301\u5b8f\uff0c\u8bf7\u5305\u542bfuncapi.h\u3002\u8fd9\u4e9b\u5b8f\u4e0e\u7ed3\u6784\u4f53FuncCallContext\u4e00\u8d77\u4f7f\u7528\uff0c\u8be5\u7ed3\u6784\u4f53\u5305\u542b\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u5b58\u7684\u72b6\u6001\u3002\u5728\u4f7f\u7528\u8fd9\u4e9b\u5b8f\u7684 SRF \u4e2d\uff0cfcinfo->flinfo->fn_extra\u7528\u4e8e\u5728\u8c03\u7528\u4e4b\u95f4\u4fdd\u5b58\u6307\u5411FuncCallContext\u7684\u6307\u9488\u3002\u5b8f\u5728\u7b2c\u4e00\u6b21\u4f7f\u7528\u65f6\u81ea\u52a8\u586b\u5145\u8be5\u5b57\u6bb5\uff0c\u5e76\u671f\u671b\u5728\u540e\u7eed\u4f7f\u7528\u4e2d\u627e\u5230\u76f8\u540c\u7684\u6307\u9488\u3002

\n
typedef struct FuncCallContext\n{\n    /*\n     * Number of times we've been called before\n     *\n     * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and\n     * incremented for you every time SRF_RETURN_NEXT() is called.\n     */\n    uint64 call_cntr;\n\n    /*\n     * OPTIONAL maximum number of calls\n     *\n     * max_calls is here for convenience only and setting it is optional.\n     * If not set, you must provide alternative means to know when the\n     * function is done.\n     */\n    uint64 max_calls;\n\n    /*\n     * OPTIONAL pointer to miscellaneous user-provided context information\n     *\n     * user_fctx is for use as a pointer to your own data to retain\n     * arbitrary context information between calls of your function.\n     */\n    void *user_fctx;\n\n    /*\n     * OPTIONAL pointer to struct containing attribute type input metadata\n     *\n     * attinmeta is for use when returning tuples (i.e., composite data types)\n     * and is not used when returning base data types. It is only needed\n     * if you intend to use BuildTupleFromCStrings() to create the return\n     * tuple.\n     */\n    AttInMetadata *attinmeta;\n\n    /*\n     * memory context used for structures that must live for multiple calls\n     *\n     * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used\n     * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory\n     * context for any memory that is to be reused across multiple calls\n     * of the SRF.\n     */\n    MemoryContext multi_call_memory_ctx;\n\n    /*\n     * OPTIONAL pointer to struct containing tuple description\n     *\n     * tuple_desc is for use when returning tuples (i.e., composite data types)\n     * and is only needed if you are going to build the tuples with\n     * heap_form_tuple() rather than with BuildTupleFromCStrings().  Note that\n     * the TupleDesc pointer stored here should usually have been run through\n     * BlessTupleDesc() first.\n     */\n    TupleDesc tuple_desc;\n\n} FuncCallContext;\n
\n

\u4f7f\u7528\u6b64\u57fa\u7840\u7ed3\u6784\u7684SRF\u5c06\u4f7f\u7528\u7684\u5b8f\u662f\uff1a

\n
SRF_IS_FIRSTCALL()\n
\n

\u6765\u5224\u65ad\u4f60\u7684\u51fd\u6570\u662f\u5426\u662f\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u3002\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff08\u53ea\u80fd\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\uff09\u4f7f\u7528\uff1a

\n
SRF_FIRSTCALL_INIT()\n
\n

\u521d\u59cb\u5316FuncCallContext\u3002\u5728\u6bcf\u6b21\u51fd\u6570\u8c03\u7528\u65f6\uff0c\u5305\u542b\u7b2c\u4e00\u6b21\uff0c\u8c03\u7528\uff1a

\n
SRF_PERCALL_SETUP()\n
\n

\u8bbe\u7f6e\u4f7f\u7528FuncCallContext\u3002

\n

\u5982\u679c\u4f60\u7684\u51fd\u6570\u5728\u5f53\u524d\u8c03\u7528\u4e2d\u6709\u6570\u636e\u8981\u8fd4\u56de\uff0c\u8bf7\u4f7f\u7528\uff1a

\n
SRF_RETURN_NEXT(funcctx, result)\n
\n

\u628a\u5b83\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\uff08result\u5fc5\u987b\u662f\u7c7b\u578bDatum\uff0c\u53ef\u4ee5\u662f\u4e00\u4e2a\u5355\u4e00\u503c\u6216\u8005\u6309\u4e0a\u6587\u6240\u8ff0\u51c6\u5907\u597d\u7684\u5143\u7ec4\uff09\u3002\u6700\u540e\uff0c\u5f53\u51fd\u6570\u5b8c\u6210\u4e86\u6570\u636e\u8fd4\u56de\u540e\uff0c\u53ef\u4f7f\u7528\uff1a

\n
SRF_RETURN_DONE(funcctx)\n
\n

\u7528\u4e8e\u6e05\u7406\u5e76\u7ed3\u675f SRF\u3002

\n

\u8c03\u7528 SRF \u65f6\u7684\u5f53\u524d\u5185\u5b58\u4e0a\u4e0b\u6587\u662f\u4e34\u65f6\u4e0a\u4e0b\u6587\uff0c\u4f1a\u5728\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u6e05\u7a7a\u3002\u56e0\u6b64\uff0c\u65e0\u9700\u5bf9\u901a\u8fc7 palloc \u5206\u914d\u7684\u6bcf\u5757\u5185\u5b58\u8c03\u7528 pfree\uff0c\u5b83\u4eec\u90fd\u4f1a\u88ab\u81ea\u52a8\u6e05\u7406\u3002\u4e0d\u8fc7\uff0c\u9700\u8981\u8de8\u8c03\u7528\u4fdd\u7559\u7684\u6570\u636e\u7ed3\u6784\u5fc5\u987b\u653e\u5728\u5176\u4ed6\u4f4d\u7f6e\u3002multi_call_memory_ctx \u6240\u5f15\u7528\u7684\u5185\u5b58\u4e0a\u4e0b\u6587\u9002\u5408\u4fdd\u5b58\u76f4\u5230 SRF \u8fd0\u884c\u7ed3\u675f\u4ecd\u9700\u4fdd\u7559\u7684\u6570\u636e\u3002\u901a\u5e38\u5e94\u5728\u9996\u6b21\u8c03\u7528\u7684\u521d\u59cb\u5316\u9636\u6bb5\u5207\u6362\u5230 multi_call_memory_ctx\uff0c\u5e76\u7528 funcctx->user_fctx \u4fdd\u5b58\u6307\u5411\u6b64\u7c7b\u8de8\u8c03\u7528\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\uff08\u5728 multi_call_memory_ctx \u4e2d\u5206\u914d\u7684\u6570\u636e\u4f1a\u5728\u67e5\u8be2\u7ed3\u675f\u65f6\u81ea\u52a8\u6e05\u7406\uff0c\u4e5f\u65e0\u9700\u624b\u52a8\u91ca\u653e\u3002\uff09

\n
\n

\u8b66\u544a

\n

\u867d\u7136\u51fd\u6570\u7684\u5b9e\u53c2\u5728\u591a\u6b21\u8c03\u7528\u4e4b\u95f4\u4fdd\u6301\u4e0d\u53d8\uff0c\u4f46\u5982\u679c\u5728\u77ac\u65f6\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u4e86\u53c2\u6570\uff08\u901a\u5e38\u7531 PG_GETARG_xxx \u5b8f\u5b8c\u6210\uff09\uff0c\u90a3\u4e48\u88ab\u53cd TOAST \u7684\u62f7\u8d1d\u5c06\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\u88ab\u91ca\u653e\u3002\u76f8\u5e94\u5730\uff0c\u5982\u679c\u4f60\u628a\u8fd9\u4e9b\u503c\u7684\u5f15\u7528\u4fdd\u5b58\u5728user_fctx\u4e2d\uff0c\u4f60\u4e5f\u5fc5\u987b\u5728\u53cd TOAST \u4e4b\u540e\u628a\u5b83\u4eec\u62f7\u8d1d\u5230 multi_call_memory_ctx\u4e2d\uff0c\u6216\u8005\u786e\u4fdd\u4f60\u53ea\u5728\u90a3\u4e2a\u4e0a\u4e0b\u6587\u4e2d\u53cd TOAST \u8fd9\u4e9b\u503c\u3002

\n
\n

\u4e00\u4e2a\u5b8c\u6574\u7684\u4f2a\u4ee3\u7801\u793a\u4f8b\uff1a

\n
Datum\nmy_set_returning_function(PG_FUNCTION_ARGS)\n{\n    FuncCallContext  *funcctx;\n    Datum             result;\n    further declarations as needed\n\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext oldcontext;\n\n        funcctx = SRF_FIRSTCALL_INIT();\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n        /* One-time setup code appears here: */\n        user code\n        if returning composite\n            build TupleDesc, and perhaps AttInMetadata\n        endif returning composite\n        user code\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* Each-time setup code appears here: */\n    user code\n    funcctx = SRF_PERCALL_SETUP();\n    user code\n\n    /* this is just one way we might test whether we are done: */\n    if (funcctx->call_cntr < funcctx->max_calls)\n    {\n        /* Here we want to return another item: */\n        user code\n        obtain result Datum\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else\n    {\n        /* Here we are done returning items, so just report that fact. */\n        /* (Resist the temptation to put cleanup code here.) */\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n
\n

\u4e00\u4e2a\u8fd4\u56de\u590d\u5408\u7c7b\u578b\u7684\u7b80\u5355SRF\u7684\u5b8c\u6574\u793a\u4f8b\u5982\u4e0b\uff1a

\n
PG_FUNCTION_INFO_V1(retcomposite);\n\nDatum\nretcomposite(PG_FUNCTION_ARGS)\n{\n    FuncCallContext     *funcctx;\n    int                  call_cntr;\n    int                  max_calls;\n    TupleDesc            tupdesc;\n    AttInMetadata       *attinmeta;\n\n    /* stuff done only on the first call of the function */\n    if (SRF_IS_FIRSTCALL())\n    {\n        MemoryContext   oldcontext;\n\n        /* create a function context for cross-call persistence */\n        funcctx = SRF_FIRSTCALL_INIT();\n\n        /* switch to memory context appropriate for multiple function calls */\n        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);\n\n        /* total number of tuples to be returned */\n        funcctx->max_calls = PG_GETARG_INT32(0);\n\n        /* Build a tuple descriptor for our result type */\n        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)\n            ereport(ERROR,\n                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),\n                     errmsg(\"function returning record called in context \"\n                            \"that cannot accept type record\")));\n\n        /*\n         * generate attribute metadata needed later to produce tuples from raw\n         * C strings\n         */\n        attinmeta = TupleDescGetAttInMetadata(tupdesc);\n        funcctx->attinmeta = attinmeta;\n\n        MemoryContextSwitchTo(oldcontext);\n    }\n\n    /* stuff done on every call of the function */\n    funcctx = SRF_PERCALL_SETUP();\n\n    call_cntr = funcctx->call_cntr;\n    max_calls = funcctx->max_calls;\n    attinmeta = funcctx->attinmeta;\n\n    if (call_cntr < max_calls)    /* do when there is more left to send */\n    {\n        char       **values;\n        HeapTuple    tuple;\n        Datum        result;\n\n        /*\n         * Prepare a values array for building the returned tuple.\n         * This should be an array of C strings which will\n         * be processed later by the type input functions.\n         */\n        values = (char **) palloc(3 * sizeof(char *));\n        values[0] = (char *) palloc(16 * sizeof(char));\n        values[1] = (char *) palloc(16 * sizeof(char));\n        values[2] = (char *) palloc(16 * sizeof(char));\n\n        snprintf(values[0], 16, \"%d\", 1 * PG_GETARG_INT32(1));\n        snprintf(values[1], 16, \"%d\", 2 * PG_GETARG_INT32(1));\n        snprintf(values[2], 16, \"%d\", 3 * PG_GETARG_INT32(1));\n\n        /* build a tuple */\n        tuple = BuildTupleFromCStrings(attinmeta, values);\n\n        /* make the tuple into a datum */\n        result = HeapTupleGetDatum(tuple);\n\n        /* clean up (this is not really necessary) */\n        pfree(values[0]);\n        pfree(values[1]);\n        pfree(values[2]);\n        pfree(values);\n\n        SRF_RETURN_NEXT(funcctx, result);\n    }\n    else    /* do when there is no more left */\n    {\n        SRF_RETURN_DONE(funcctx);\n    }\n}\n\n
\n

\u5728SQL\u4e2d\u58f0\u660e\u6b64\u51fd\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\uff1a

\n
CREATE TYPE __retcomposite AS (f1 integer, f2 integer, f3 integer);\n\nCREATE OR REPLACE FUNCTION retcomposite(integer, integer)\n    RETURNS SETOF __retcomposite\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u4f7f\u7528OUT\u53c2\u6570\uff1a

\n
CREATE OR REPLACE FUNCTION retcomposite(IN integer, IN integer,\n    OUT f1 integer, OUT f2 integer, OUT f3 integer)\n    RETURNS SETOF record\n    AS 'filename', 'retcomposite'\n    LANGUAGE C IMMUTABLE STRICT;\n
\n

\u8bf7\u6ce8\u610f\uff0c\u91c7\u7528\u8fd9\u79cd\u65b9\u6cd5\u65f6\uff0c\u51fd\u6570\u7684\u8f93\u51fa\u7c7b\u578b\u5728\u5f62\u5f0f\u4e0a\u662f\u4e00\u4e2a\u533f\u540d\u7684 record \u7c7b\u578b\u3002

\n
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\n
\n
\n
\n

36.10.10. \u591a\u6001\u53c2\u6570\u548c\u8fd4\u56de\u7c7b\u578b

\n
\n
\n
\n

\u53ef\u4ee5\u58f0\u660e C \u8bed\u8a00\u51fd\u6570\u6765\u63a5\u53d7\u548c\u8fd4\u56de\u7b2c\u00a036.2.5\u00a0\u8282\u4e2d\u63cf\u8ff0\u7684\u591a\u6001\u7c7b\u578b\u3002\u5f53\u51fd\u6570\u53c2\u6570\u6216\u8005\u8fd4\u56de\u7c7b\u578b\u88ab\u5b9a\u4e49\u4e3a\u591a\u6001\u7c7b\u578b\u65f6\uff0c\u51fd\u6570\u7684\u7f16\u5199\u8005\u65e0\u6cd5\u63d0\u524d\u77e5\u9053\u4f1a\u7528\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u8c03\u7528\u8be5\u51fd\u6570\u6216\u8005\u8be5\u51fd\u6570\u9700\u8981\u8fd4\u56de\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002\u5728fmgr.h \u4e2d\u63d0\u4f9b\u4e86\u4e24\u79cd\u4f8b\u7a0b\u6765\u5141\u8bb8\u7248\u672c-1 \u7684 C \u51fd\u6570\u53d1\u73b0\u5176\u53c2\u6570\u7684\u5b9e\u9645\u6570\u636e\u7c7b\u578b\u4ee5\u53ca\u5b83\u8981\u8fd4\u56de\u7684\u7c7b\u578b\u3002\u8fd9\u4e9b\u4f8b\u7a0b\u88ab\u79f0\u4e3a get_fn_expr_rettype(FmgrInfo *flinfo)\u548c get_fn_expr_argtype(FmgrInfo *flinfo, int argnum)\u3002\u5b83\u4eec\u8fd4\u56de\u7ed3\u679c\u6216\u8005\u53c2\u6570\u7684\u7c7b\u578b\u7684 OID\uff0c\u6216\u8005\u5f53\u8be5\u4fe1\u606f\u4e0d\u53ef\u7528\u65f6\u8fd4\u56de InvalidOid\u3002\u7ed3\u6784\u4f53flinfo\u901a\u5e38\u88ab\u5f53\u505a fcinfo->flinfo\u8bbf\u95ee\u3002\u53c2\u6570argnum\u5219\u662f\u4ece\u96f6\u5f00\u59cb\u8ba1\u3002get_call_result_type\u4e5f\u53ef\u88ab\u7528\u4f5c get_fn_expr_rettype\u7684\u4e00\u79cd\u66ff\u4ee3\u54c1\u3002\u8fd8\u6709 get_fn_expr_variadic\uff0c\u5b83\u53ef\u4ee5\u88ab\u7528\u6765\u627e\u51fa\u53ef\u53d8\u53c2\u6570\u662f\u5426\u5df2\u7ecf\u88ab\u5408\u5e76\u5230\u4e86\u4e00\u4e2a\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e3b\u8981\u7528\u4e8e VARIADIC \"any\"\u51fd\u6570\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u63a5\u6536\u666e\u901a\u6570\u7ec4\u7c7b\u578b\u7684\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u6765\u8bf4\u603b\u662f\u4f1a\u53d1\u751f\u8fd9\u7c7b\u5408\u5e76\u3002

\n

\u4f8b\u5982\uff0c\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u5199\u4e00\u4e2a\u63a5\u6536\u4e00\u4e2a\u4efb\u610f\u7c7b\u578b\u5143\u7d20\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u8be5\u7c7b\u578b\u7684\u4e00\u7ef4\u6570\u7ec4\u7684\u51fd\u6570\uff1a

\n
PG_FUNCTION_INFO_V1(make_array);\nDatum\nmake_array(PG_FUNCTION_ARGS)\n{\n    ArrayType  *result;\n    Oid         element_type = get_fn_expr_argtype(fcinfo->flinfo, 0);\n    Datum       element;\n    bool        isnull;\n    int16       typlen;\n    bool        typbyval;\n    char        typalign;\n    int         ndims;\n    int         dims[MAXDIM];\n    int         lbs[MAXDIM];\n\n    if (!OidIsValid(element_type))\n        elog(ERROR, \"could not determine data type of input\");\n\n    /* get the provided element, being careful in case it's NULL */\n    isnull = PG_ARGISNULL(0);\n    if (isnull)\n        element = (Datum) 0;\n    else\n        element = PG_GETARG_DATUM(0);\n\n    /* we have one dimension */\n    ndims = 1;\n    /* and one element */\n    dims[0] = 1;\n    /* and lower bound is 1 */\n    lbs[0] = 1;\n\n    /* get required info about the element type */\n    get_typlenbyvalalign(element_type, &typlen, &typbyval, &typalign);\n\n    /* now build the array */\n    result = construct_md_array(&element, &isnull, ndims, dims, lbs,\n                                element_type, typlen, typbyval, typalign);\n\n    PG_RETURN_ARRAYTYPE_P(result);\n}\n
\n

\u4e0b\u9762\u7684\u547d\u4ee4\u5728 SQL \u4e2d\u58f0\u660e\u4e86 make_array \u51fd\u6570\uff1a

\n
CREATE FUNCTION make_array(anyelement) RETURNS anyarray\n    AS 'DIRECTORY/funcs', 'make_array'\n    LANGUAGE C IMMUTABLE;\n
\n

\u8fd8\u6709\u4e00\u79cd\u53ea\u5bf9 C \u8bed\u8a00\u51fd\u6570\u53ef\u7528\u7684\u591a\u6001\u53d8\u4f53\uff1a\u5b83\u4eec\u53ef\u4ee5\u88ab\u58f0\u660e\u4e3a\u63a5\u53d7 \"any\" \u7c7b\u578b\u7684\u53c2\u6570\u3002\uff08\u6ce8\u610f\uff0c\u8fd9\u4e2a\u7c7b\u578b\u540d\u5fc5\u987b\u7528\u53cc\u5f15\u53f7\u62ec\u8d77\u6765\uff0c\u56e0\u4e3a\u5b83\u540c\u65f6\u4e5f\u662f SQL \u4fdd\u7559\u5b57\u3002\uff09\u5b83\u4e0e anyelement \u7c7b\u4f3c\uff0c\u4f46\u4e0d\u4f1a\u8981\u6c42\u4e0d\u540c\u7684 \"any\" \u53c2\u6570\u5fc5\u987b\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u4e5f\u4e0d\u4f1a\u5e2e\u52a9\u786e\u5b9a\u51fd\u6570\u7684\u7ed3\u679c\u7c7b\u578b\u3002C \u8bed\u8a00\u51fd\u6570\u8fd8\u53ef\u4ee5\u628a\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u58f0\u660e\u4e3a VARIADIC \"any\"\u3002\u8fd9\u53ef\u4ee5\u5339\u914d\u4e00\u4e2a\u6216\u591a\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5b9e\u53c2\uff08\u4e0d\u5fc5\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff09\u3002\u8fd9\u4e9b\u53c2\u6570\u4e0d\u4f1a\u50cf\u666e\u901a\u53ef\u53d8\u53c2\u6570\u51fd\u6570\u90a3\u6837\u88ab\u6536\u96c6\u6210\u4e00\u4e2a\u6570\u7ec4\uff0c\u800c\u662f\u4f1a\u5355\u72ec\u4f20\u7ed9\u51fd\u6570\u3002\u4f7f\u7528\u8fd9\u79cd\u7279\u6027\u65f6\uff0c\u5fc5\u987b\u7ed3\u5408 PG_NARGS() \u5b8f\u4ee5\u53ca\u524d\u9762\u4ecb\u7ecd\u7684\u65b9\u6cd5\u6765\u786e\u5b9a\u5b9e\u53c2\u7684\u4e2a\u6570\u548c\u7c7b\u578b\u3002\u6b64\u5916\uff0c\u8fd9\u79cd\u51fd\u6570\u7684\u7528\u6237\u4e5f\u53ef\u80fd\u5e0c\u671b\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528 VARIADIC \u5173\u952e\u5b57\uff0c\u4ee5\u4fbf\u8ba9\u51fd\u6570\u628a\u6570\u7ec4\u5143\u7d20\u5f53\u4f5c\u72ec\u7acb\u53c2\u6570\u5904\u7406\u3002\u5982\u679c\u5e0c\u671b\u652f\u6301\u8fd9\u79cd\u884c\u4e3a\uff0c\u51fd\u6570\u672c\u8eab\u5c31\u5fc5\u987b\u5728\u4f7f\u7528 get_fn_expr_variadic \u68c0\u6d4b\u5230\u5b9e\u53c2\u88ab\u6807\u8bb0\u4e3a VARIADIC \u540e\u81ea\u884c\u5b9e\u73b0\u5b83\u3002

\n
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\n
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\n

36.10.11. \u5171\u4eab\u5185\u5b58

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36.10.11.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

\n
\n
\n

\n
\n
\n
\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u3002\u4e3a\u6b64\uff0c\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\uff0c\u5e76\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\u3002\u6b64\u94a9\u5b50\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559\u5171\u4eab\u5185\u5b58\uff1a

\n
void RequestAddinShmemSpace(Size size)\n
\n

\u6765\u9884\u7559\u5171\u4eab\u5185\u5b58\u3002\u6bcf\u4e2a\u540e\u7aef\u90fd\u5e94\u5f53\u901a\u8fc7\u8c03\u7528\uff1a

\n
void *ShmemInitStruct(const char *name, Size size, bool *foundPtr)\n
\n

\u6765\u83b7\u53d6\u6307\u5411\u8fd9\u5757\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u6307\u9488\u3002\u5982\u679c\u8be5\u51fd\u6570\u628a foundPtr \u8bbe\u4e3a false\uff0c\u8c03\u7528\u8005\u5c31\u5e94\u521d\u59cb\u5316\u8fd9\u5757\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u5185\u5bb9\uff1b\u5982\u679c foundPtr \u4e3a true\uff0c\u8bf4\u660e\u8be5\u5171\u4eab\u5185\u5b58\u5df2\u7ecf\u7531\u5176\u4ed6\u540e\u7aef\u521d\u59cb\u5316\u8fc7\uff0c\u8c03\u7528\u8005\u65e0\u9700\u518d\u505a\u521d\u59cb\u5316\u3002

\n

\u4e3a\u907f\u514d\u7ade\u4e89\u6761\u4ef6\uff0c\u6bcf\u4e2a\u540e\u7aef\u5728\u521d\u59cb\u5316\u5176\u5171\u4eab\u5185\u5b58\u5206\u914d\u65f6\u90fd\u5e94\u4f7f\u7528 LWLock AddinShmemInitLock\uff0c\u5982\u4e0b\u6240\u793a\uff1a

\n
static mystruct *ptr = NULL;\nbool        found;\n\nLWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);\nptr = ShmemInitStruct(\"my struct name\", size, &found);\nif (!found)\n{\n    ... initialize contents of shared memory ...\n    ptr->locks = GetNamedLWLockTranche(\"my tranche name\");\n}\nLWLockRelease(AddinShmemInitLock);\n
\n

shmem_startup_hook \u4e3a\u521d\u59cb\u5316\u4ee3\u7801\u63d0\u4f9b\u4e86\u4e00\u4e2a\u65b9\u4fbf\u7684\u4f4d\u7f6e\uff0c\u4f46\u5e76\u4e0d\u5f3a\u5236\u8981\u6c42\u6240\u6709\u8fd9\u7c7b\u4ee3\u7801\u90fd\u653e\u5728\u8fd9\u4e2a\u94a9\u5b50\u4e2d\u3002\u5728 Windows \u4e0a\uff08\u4ee5\u53ca\u4efb\u4f55\u5b9a\u4e49\u4e86 EXEC_BACKEND \u7684\u5e73\u53f0\u4e0a\uff09\uff0c\u6bcf\u4e2a\u540e\u7aef\u90fd\u4f1a\u5728\u9644\u52a0\u5230\u5171\u4eab\u5185\u5b58\u540e\u4e0d\u4e45\u6267\u884c\u5df2\u6ce8\u518c\u7684 shmem_startup_hook\uff0c\u56e0\u6b64\u63d2\u4ef6\u5728\u8be5\u94a9\u5b50\u4e2d\u4ecd\u5e94\u50cf\u4e0a\u4f8b\u90a3\u6837\u83b7\u53d6 AddinShmemInitLock\u3002\u5728\u5176\u4ed6\u5e73\u53f0\u4e0a\uff0c\u53ea\u6709 postmaster \u8fdb\u7a0b\u4f1a\u6267\u884c shmem_startup_hook\uff0c\u6bcf\u4e2a\u540e\u7aef\u4f1a\u81ea\u52a8\u7ee7\u627f\u8fd9\u4e9b\u5171\u4eab\u5185\u5b58\u6307\u9488\u3002

\n

shmem_request_hook \u4e0e shmem_startup_hook \u7684\u4e00\u4e2a\u5b8c\u6574\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_stat_statements/pg_stat_statements.c\u3002

\n
\n
\n
\n
\n
\n

\n
\n
\n

36.10.11.2.\u00a0\u542f\u52a8\u540e\u8bf7\u6c42\u5171\u4eab\u5185\u5b58

\n
\n
\n

\n
\n
\n
\n

\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u9884\u7559\u5171\u4eab\u5185\u5b58\u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u4e4b\u540e\uff0c\u5e76\u4e14\u65e0\u9700\u501f\u52a9 shmem_request_hook \u6765\u5b8c\u6210\u3002\u4e3a\u6b64\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8be5\u5171\u4eab\u5185\u5b58\u7684\u540e\u7aef\u90fd\u5e94\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u83b7\u53d6\u4e00\u4e2a\u6307\u9488\uff1a

\n
void *GetNamedDSMSegment(const char *name, size_t size,\n                         void (*init_callback) (void *ptr),\n                         bool *found)\n
\n

\u5982\u679c\u7ed9\u5b9a\u540d\u79f0\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u5c1a\u4e0d\u5b58\u5728\uff0c\u8be5\u51fd\u6570\u4f1a\u5206\u914d\u8be5\u6bb5\uff0c\u5e76\u4f7f\u7528\u63d0\u4f9b\u7684 init_callback \u56de\u8c03\u51fd\u6570\u5bf9\u5176\u8fdb\u884c\u521d\u59cb\u5316\u3002\u5982\u679c\u8be5\u6bb5\u5df2\u7ecf\u7531\u53e6\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8fc7\uff0c\u8be5\u51fd\u6570\u5c31\u53ea\u4f1a\u628a\u73b0\u6709\u7684\u52a8\u6001\u5171\u4eab\u5185\u5b58\u6bb5\u9644\u52a0\u5230\u5f53\u524d\u540e\u7aef\u3002

\n

\u4e0e\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559\u7684\u5171\u4eab\u5185\u5b58\u4e0d\u540c\uff0c\u4f7f\u7528 GetNamedDSMSegment \u9884\u7559\u5171\u4eab\u5185\u5b58\u65f6\uff0c\u65e0\u9700\u83b7\u53d6 AddinShmemInitLock\uff0c\u4e5f\u65e0\u9700\u91c7\u53d6\u5176\u4ed6\u63aa\u65bd\u907f\u514d\u7ade\u6001\u6761\u4ef6\u3002\u6b64\u51fd\u6570\u4fdd\u8bc1\u4ec5\u7531\u4e00\u4e2a\u540e\u7aef\u5206\u914d\u5e76\u521d\u59cb\u5316\u8be5\u6bb5\uff0c\u5176\u4ed6\u6240\u6709\u540e\u7aef\u83b7\u5f97\u7684\u90fd\u662f\u6307\u5411\u5df2\u5b8c\u5168\u5206\u914d\u5e76\u521d\u59cb\u5316\u7684\u6bb5\u7684\u6307\u9488\u3002

\n

GetNamedDSMSegment \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/test_dsm_registry/test_dsm_registry.c\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n
\n
\n
\n
\n
\n
\n

36.10.12. \u8f7b\u91cf\u7ea7\u9501\uff08LWLocks\uff09

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36.10.12.1.\u00a0\u542f\u52a8\u65f6\u8bf7\u6c42 LWLocks

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\n

\u9644\u52a0\u6a21\u5757\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u65f6\u9884\u7559 LWLocks\u3002\u4e0e\u542f\u52a8\u65f6\u9884\u7559\u5171\u4eab\u5185\u5b58\u4e00\u6837\uff0c\u5fc5\u987b\u901a\u8fc7 shared_preload_libraries \u9884\u52a0\u8f7d\u6a21\u5757\u7684\u5171\u4eab\u5e93\uff0c\u5e76\u5728\u5176 _PG_init \u51fd\u6570\u4e2d\u6ce8\u518c shmem_request_hook\u3002\u6b64\u94a9\u5b50\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u9884\u7559 LWLocks\uff1a

\n
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)\n
\n

\u8fd9\u786e\u4fdd\u5b58\u5728\u4e00\u4e2a\u540d\u4e3a tranche_name\u3001\u5305\u542b num_lwlocks \u4e2a LWLocks \u7684\u6570\u7ec4\u3002\u53ef\u901a\u8fc7\u4ee5\u4e0b\u8c03\u7528\u53d6\u5f97\u8be5\u6570\u7ec4\u7684\u6307\u9488\uff1a

\n
LWLockPadded *GetNamedLWLockTranche(const char *tranche_name)\n
\n
\n
\n
\n
\n
\n

\n
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\n

36.10.12.2.\u00a0\u542f\u52a8\u540e\u8bf7\u6c42 LWLocks

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\n
\n

\u8fd8\u6709\u53e6\u4e00\u79cd\u66f4\u7075\u6d3b\u7684\u83b7\u53d6 LWLocks \u7684\u65b9\u6cd5\uff0c\u53ef\u4ee5\u5728\u670d\u52a1\u5668\u542f\u52a8\u540e\u8fdb\u884c\uff0c\u4e5f\u65e0\u9700\u501f\u52a9 shmem_request_hook\u3002\u4e3a\u6b64\uff0c\u9996\u5148\u901a\u8fc7\u8c03\u7528\u4e0b\u9762\u7684\u51fd\u6570\u5206\u914d\u4e00\u4e2a tranche_id\uff1a

\n
int LWLockNewTrancheId(void)\n
\n

\u63a5\u4e0b\u6765\uff0c\u521d\u59cb\u5316\u6bcf\u4e2a LWLock\uff0c\u5e76\u628a\u65b0\u7684 tranche_id \u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\uff1a

\n
void LWLockInitialize(LWLock *lock, int tranche_id)\n
\n

\u4e0e\u5171\u4eab\u5185\u5b58\u7c7b\u4f3c\uff0c\u6bcf\u4e2a\u540e\u7aef\u90fd\u5e94\u786e\u4fdd\u53ea\u6709\u4e00\u4e2a\u8fdb\u7a0b\u4f1a\u5206\u914d\u65b0\u7684 tranche_id \u5e76\u521d\u59cb\u5316\u6bcf\u4e00\u4e2a\u65b0\u7684 LWLock\u3002\u4e00\u79cd\u505a\u6cd5\u662f\u4ec5\u5728\u6301\u6709 AddinShmemInitLock \u72ec\u5360\u9501\u7684\u5171\u4eab\u5185\u5b58\u521d\u59cb\u5316\u4ee3\u7801\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u3002\u5982\u679c\u4f7f\u7528 GetNamedDSMSegment\uff0c\u90a3\u4e48\u5728 init_callback \u56de\u8c03\u51fd\u6570\u4e2d\u8c03\u7528\u8fd9\u4e9b\u51fd\u6570\u5c31\u8db3\u4ee5\u907f\u514d\u7ade\u4e89\u6761\u4ef6\u3002

\n

\u6700\u540e\uff0c\u6bcf\u4e2a\u4f7f\u7528\u8be5 tranche_id \u7684\u540e\u7aef\u90fd\u5e94\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u628a\u5b83\u4e0e\u4e00\u4e2a tranche_name \u5173\u8054\u8d77\u6765\uff1a

\n
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)\n
\n

LWLockNewTrancheId\u3001LWLockInitialize \u548c LWLockRegisterTranche \u7684\u5b8c\u6574\u4f7f\u7528\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 contrib/pg_prewarm/autoprewarm.c\u3002

\n
\n
\n
\n
\n
\n
\n

36.10.13. \u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6

\n
\n
\n
\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u5728\u7b49\u5f85\u4e8b\u4ef6\u7c7b\u578b Extension \u4e0b\u5b9a\u4e49\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\uff1a

\n
uint32 WaitEventExtensionNew(const char *wait_event_name)\n
\n

\u8be5\u7b49\u5f85\u4e8b\u4ef6\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u9762\u5411\u7528\u6237\u7684\u81ea\u5b9a\u4e49\u5b57\u7b26\u4e32\u3002\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/worker_spi\uff0c\u4f4d\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u3002

\n

\u81ea\u5b9a\u4e49\u7b49\u5f85\u4e8b\u4ef6\u53ef\u4ee5\u5728 pg_stat_activity \u4e2d\u67e5\u770b\uff1a

\n
=# SELECT wait_event_type, wait_event FROM pg_stat_activity\n     WHERE backend_type ~ 'worker_spi';\n wait_event_type |  wait_event\n-----------------+---------------\n Extension       | WorkerSpiMain\n(1 row)\n
\n
\n
\n
\n
\n
\n

36.10.14. \u6ce8\u5165\u70b9

\n
\n
\n
\n

\u7ed9\u5b9a\u540d\u79f0 name \u7684\u6ce8\u5165\u70b9\u53ef\u901a\u8fc7\u4ee5\u4e0b\u5b8f\u58f0\u660e\uff1a

\n
INJECTION_POINT(name, arg);\n
\n

\u670d\u52a1\u5668\u4ee3\u7801\u4e2d\u5df2\u7ecf\u5728\u82e5\u5e72\u5173\u952e\u4f4d\u7f6e\u58f0\u660e\u4e86\u6ce8\u5165\u70b9\u3002\u65b0\u589e\u6ce8\u5165\u70b9\u540e\uff0c\u9700\u8981\u91cd\u65b0\u7f16\u8bd1\u4ee3\u7801\uff0c\u624d\u80fd\u8ba9\u8be5\u6ce8\u5165\u70b9\u51fa\u73b0\u5728\u4e8c\u8fdb\u5236\u6587\u4ef6\u4e2d\u3002\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u4e5f\u53ef\u4ee5\u4f7f\u7528\u540c\u4e00\u4e2a\u5b8f\u5728\u81ea\u5df1\u7684\u4ee3\u7801\u4e2d\u58f0\u660e\u6ce8\u5165\u70b9\u3002\u6ce8\u5165\u70b9\u540d\u79f0\u5e94\u4f7f\u7528\u5c0f\u5199\u5b57\u6bcd\uff0c\u5e76\u7528\u8fde\u5b57\u7b26\u5206\u9694\u5404\u4e2a\u672f\u8bed\u3002arg \u662f\u8fd0\u884c\u65f6\u4f20\u7ed9\u56de\u8c03\u7684\u53ef\u9009\u53c2\u6570\u503c\u3002

\n

\u6267\u884c\u6ce8\u5165\u70b9\u53ef\u80fd\u9700\u8981\u5206\u914d\u5c11\u91cf\u5185\u5b58\uff0c\u800c\u8fd9\u53ef\u80fd\u5931\u8d25\u3002\u5982\u679c\u4f60\u9700\u8981\u5728\u4e00\u4e2a\u4e0d\u5141\u8bb8\u52a8\u6001\u5206\u914d\u7684\u4e34\u754c\u533a\u4e2d\u4f7f\u7528\u6ce8\u5165\u70b9\uff0c\u53ef\u4ee5\u91c7\u7528\u4ee5\u4e0b\u4e24\u6b65\u6cd5\uff1a

\n
INJECTION_POINT_LOAD(name);\nINJECTION_POINT_CACHED(name, arg);\n
\n

\u5728\u8fdb\u5165\u4e34\u754c\u533a\u4e4b\u524d\uff0c\u8c03\u7528 INJECTION_POINT_LOAD\u3002\u5b83\u4f1a\u68c0\u67e5\u5171\u4eab\u5185\u5b58\u72b6\u6001\uff0c\u5e76\u5728\u8be5\u6ce8\u5165\u70b9\u5904\u4e8e\u6fc0\u6d3b\u72b6\u6001\u65f6\u628a\u56de\u8c03\u52a0\u8f7d\u5230\u540e\u7aef\u79c1\u6709\u5185\u5b58\u4e2d\u3002\u5728\u4e34\u754c\u533a\u5185\u90e8\uff0c\u518d\u7528 INJECTION_POINT_CACHED \u6765\u6267\u884c\u56de\u8c03\u3002

\n

\u63d2\u4ef6\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\uff0c\u4e3a\u4e00\u4e2a\u5df2\u7ecf\u58f0\u660e\u597d\u7684\u6ce8\u5165\u70b9\u9644\u52a0\u56de\u8c03\uff1a

\n
extern void InjectionPointAttach(const char *name,\n                                 const char *library,\n                                 const char *function,\n                                 const void *private_data,\n                                 int private_data_size);\n
\n

name \u662f\u6ce8\u5165\u70b9\u7684\u540d\u79f0\uff1b\u6267\u884c\u5230\u8fbe\u6b64\u6ce8\u5165\u70b9\u65f6\uff0c\u5c06\u6267\u884c\u4ece library \u52a0\u8f7d\u7684\u51fd\u6570\u3002private_data \u662f\u4e00\u5757\u5927\u5c0f\u4e3a private_data_size \u7684\u79c1\u6709\u6570\u636e\u533a\u57df\uff0c\u5728\u6267\u884c\u56de\u8c03\u65f6\u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\u3002

\n

\u4e0b\u9762\u662f\u4e00\u4e2a InjectionPointCallback \u7684\u793a\u4f8b\uff1a

\n
static void\ncustom_injection_callback(const char *name,\n                          const void *private_data,\n                          void *arg)\n{\n    uint32 wait_event_info = WaitEventInjectionPointNew(name);\n\n    pgstat_report_wait_start(wait_event_info);\n    elog(NOTICE, \"%s: executed custom callback\", name);\n    pgstat_report_wait_end();\n}\n
\n

\u8fd9\u4e2a\u56de\u8c03\u4f1a\u4ee5 NOTICE \u7ea7\u522b\u5411\u670d\u52a1\u5668\u9519\u8bef\u65e5\u5fd7\u5199\u5165\u4e00\u6761\u6d88\u606f\uff0c\u4f46\u56de\u8c03\u5b8c\u5168\u53ef\u4ee5\u5b9e\u73b0\u66f4\u590d\u6742\u7684\u903b\u8f91\u3002

\n

\u53e6\u4e00\u79cd\u5b9a\u4e49\u201c\u5230\u8fbe\u6ce8\u5165\u70b9\u65f6\u5e94\u6267\u884c\u4ec0\u4e48\u52a8\u4f5c\u201d\u7684\u65b9\u5f0f\uff0c\u662f\u628a\u6d4b\u8bd5\u4ee3\u7801\u76f4\u63a5\u5199\u5728\u5e38\u89c4\u6e90\u4ee3\u7801\u65c1\u8fb9\u3002\u5982\u679c\u8be5\u52a8\u4f5c\u4f9d\u8d56\u4e8e\u52a0\u8f7d\u6a21\u5757\u65e0\u6cd5\u8bbf\u95ee\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u8fd9\u4f1a\u5f88\u6709\u7528\u3002\u6b64\u65f6\u53ef\u4ee5\u4f7f\u7528 IS_INJECTION_POINT_ATTACHED \u5b8f\u6765\u68c0\u67e5\u67d0\u4e2a\u6ce8\u5165\u70b9\u662f\u5426\u5df2\u9644\u52a0\uff0c\u4f8b\u5982\uff1a

\n
#ifdef USE_INJECTION_POINTS\nif (IS_INJECTION_POINT_ATTACHED(\"before-foobar\"))\n{\n    /* change a local variable if injection point is attached */\n    local_var = 123;\n\n    /* also execute the callback */\n    INJECTION_POINT_CACHED(\"before-foobar\", NULL);\n}\n#endif\n
\n

\u6ce8\u610f\uff0c\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u4e0a\u7684\u56de\u8c03\u4e0d\u4f1a\u7531 IS_INJECTION_POINT_ATTACHED \u5b8f\u6267\u884c\u3002\u5982\u679c\u4f60\u60f3\u6267\u884c\u8be5\u56de\u8c03\uff0c\u5c31\u5fc5\u987b\u50cf\u4e0a\u9762\u7684\u793a\u4f8b\u90a3\u6837\u53e6\u5916\u8c03\u7528 INJECTION_POINT_CACHED\u3002

\n

\u53ef\u9009\u5730\uff0c\u4e5f\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528\u4ee5\u4e0b\u51fd\u6570\u6765\u89e3\u9664\u4e00\u4e2a\u6ce8\u5165\u70b9\uff1a

\n
extern bool InjectionPointDetach(const char *name);\n
\n

\u6210\u529f\u65f6\u8fd4\u56de true\uff0c\u5426\u5219\u8fd4\u56de false\u3002

\n

\u4e00\u4e2a\u9644\u52a0\u5230\u6ce8\u5165\u70b9\u7684\u56de\u8c03\u4f1a\u5728\u6240\u6709\u540e\u7aef\u4e2d\u751f\u6548\uff0c\u5305\u62ec\u5728\u8c03\u7528 InjectionPointAttach \u4e4b\u540e\u624d\u542f\u52a8\u7684\u540e\u7aef\u3002\u5b83\u4f1a\u4e00\u76f4\u4fdd\u6301\u9644\u52a0\u72b6\u6001\uff0c\u76f4\u5230\u670d\u52a1\u5668\u505c\u6b62\uff0c\u6216\u8005\u901a\u8fc7 InjectionPointDetach \u5c06\u5176\u89e3\u9664\u3002

\n

\u76f8\u5173\u793a\u4f8b\u53ef\u89c1\u4e8e PostgreSQL \u6e90\u4ee3\u7801\u6811\u4e2d\u7684 src/test/modules/injection_points\u3002

\n

\u8981\u542f\u7528\u6ce8\u5165\u70b9\uff0c\u4f7f\u7528 configure \u65f6\u9700\u6307\u5b9a --enable-injection-points\uff0c\u4f7f\u7528 Meson \u65f6\u9700\u6307\u5b9a -Dinjection_points=true\u3002

\n
\n
\n
\n
\n
\n

36.10.15. \u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1

\n
\n
\n
\n

\u7528 C \u8bed\u8a00\u7f16\u5199\u7684\u63d2\u4ef6\u53ef\u4ee5\u4f7f\u7528\u5728\u7d2f\u8ba1\u7edf\u8ba1\u7cfb\u7edf\u4e2d\u6ce8\u518c\u7684\u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1\u7c7b\u578b\u3002

\n

\u9996\u5148\uff0c\u5b9a\u4e49\u4e00\u4e2a PgStat_KindInfo\uff0c\u5176\u4e2d\u5305\u542b\u4e0e\u6240\u6ce8\u518c\u81ea\u5b9a\u4e49\u7c7b\u578b\u76f8\u5173\u7684\u5168\u90e8\u4fe1\u606f\u3002\u4f8b\u5982\uff1a

\n
static const PgStat_KindInfo custom_stats = {\n    .name = \"custom_stats\",\n    .fixed_amount = false,\n    .shared_size = sizeof(PgStatShared_Custom),\n    .shared_data_off = offsetof(PgStatShared_Custom, stats),\n    .shared_data_len = sizeof(((PgStatShared_Custom *) 0)->stats),\n    .pending_size = sizeof(PgStat_StatCustomEntry),\n}\n
\n

\u7136\u540e\uff0c\u6bcf\u4e2a\u9700\u8981\u4f7f\u7528\u8fd9\u79cd\u81ea\u5b9a\u4e49\u7c7b\u578b\u7684\u540e\u7aef\uff0c\u90fd\u9700\u8981\u4f7f\u7528 pgstat_register_kind \u6ce8\u518c\u5b83\uff0c\u5e76\u6307\u5b9a\u4e00\u4e2a\u7528\u4e8e\u5b58\u50a8\u8be5\u7c7b\u7edf\u8ba1\u6761\u76ee\u7684\u552f\u4e00 ID\uff1a

\n
extern PgStat_Kind pgstat_register_kind(PgStat_Kind kind,\n                                        const PgStat_KindInfo *kind_info);\n
\n

\u5728\u5f00\u53d1\u65b0\u6269\u5c55\u65f6\uff0c\u5e94\u5c06 PGSTAT_KIND_EXPERIMENTAL \u7528\u4f5c kind\u3002\u5f53\u4f60\u51c6\u5907\u628a\u6269\u5c55\u53d1\u5e03\u7ed9\u7528\u6237\u65f6\uff0c\u8bf7\u5728 Custom Cumulative Statistics \u9875\u9762\u4e0a\u9884\u7559\u4e00\u4e2a kind ID\u3002

\n

\u5173\u4e8e PgStat_KindInfo API \u7684\u7ec6\u8282\uff0c\u53ef\u89c1 src/include/utils/pgstat_internal.h\u3002

\n

\u5df2\u6ce8\u518c\u7684\u7edf\u8ba1\u7c7b\u578b\u4f1a\u5173\u8054\u5230\u4e00\u4e2a\u540d\u79f0\u4ee5\u53ca\u4e00\u4e2a\u5728\u5171\u4eab\u5185\u5b58\u4e2d\u4f9b\u6574\u4e2a\u670d\u52a1\u5668\u5171\u4eab\u7684\u552f\u4e00 ID\u3002\u6bcf\u4e2a\u4f7f\u7528\u81ea\u5b9a\u4e49\u7edf\u8ba1\u7c7b\u578b\u7684\u540e\u7aef\u90fd\u4f1a\u7ef4\u62a4\u4e00\u4e2a\u672c\u5730\u7f13\u5b58\uff0c\u7528\u6765\u4fdd\u5b58\u5404\u4e2a\u81ea\u5b9a\u4e49 PgStat_KindInfo \u7684\u4fe1\u606f\u3002

\n

\u5e94\u5c06\u5b9e\u73b0\u81ea\u5b9a\u4e49\u7d2f\u8ba1\u7edf\u8ba1\u7c7b\u578b\u7684\u6269\u5c55\u6a21\u5757\u52a0\u5165shared_preload_libraries\uff0c\u4ee5\u4fbf\u5728 PostgreSQL \u542f\u52a8\u671f\u95f4\u5c3d\u65e9\u8f7d\u5165\u3002

\n

\u5c55\u793a\u5982\u4f55\u6ce8\u518c\u5e76\u4f7f\u7528\u81ea\u5b9a\u4e49\u7edf\u8ba1\u4fe1\u606f\u7684\u793a\u4f8b\u53ef\u89c1\u4e8e src/test/modules/injection_points\u3002

\n
\n
\n
\n
\n
\n

36.10.16. \u628a C++ \u7528\u4e8e\u53ef\u6269\u5c55\u6027

\n
\n
\n
\n

\u5c3d\u7ba1PostgreSQL\u540e\u7aef\u662f\u7528 C \u7f16\u5199\u7684\uff0c\u53ea\u8981\u9075\u5faa\u4e0b\u9762\u7684\u6307\u5bfc\u65b9\u9488\u4e5f\u53ef\u4ee5\u7528 C++ \u7f16\u5199\u6269\u5c55\uff1a

\n
\n
    \n
  • \n

    \u6240\u6709\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u5fc5\u987b\u5bf9\u540e\u7aef\u5448\u73b0\u4e00\u79cd C \u63a5\u53e3\uff0c\u7136\u540e\u8fd9\u4e9b C \u51fd\u6570\u8c03\u7528 C++ \u51fd\u6570\u3002\u4f8b\u5982\uff0c\u88ab\u540e\u7aef\u8bbf\u95ee\u7684\u51fd\u6570\u8981\u6c42extern C \u94fe\u63a5\u3002\u5bf9\u9700\u8981\u5728\u540e\u7aef\u548c C++ \u4ee3\u7801\u4e4b\u95f4\u4f5c\u4e3a\u6307\u9488\u4f20\u9012\u7684\u4efb\u4f55\u51fd\u6570\u4e5f\u8981\u8fd9\u6837\u505a\u3002

    \n
    • \n
  • \n

    \u4f7f\u7528\u5408\u9002\u7684\u91ca\u653e\u65b9\u6cd5\u91ca\u653e\u5185\u5b58\u3002\u4f8b\u5982\uff0c\u5927\u90e8\u5206\u540e\u7aef\u5185\u5b58\u662f\u901a\u8fc7 palloc()\u5206\u914d\u7684\uff0c\u6240\u4ee5\u5e94\u4f7f\u7528pfree() \u6765\u91ca\u653e\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e2d\u4f7f\u7528 C++ \u7684delete\u4f1a\u5931\u8d25\u3002

    \n
    • \n
  • \n

    \u9632\u6b62\u5f02\u5e38\u4f20\u64ad\u5230 C \u4ee3\u7801\u4e2d\uff08\u5728\u6240\u6709extern C\u51fd\u6570\u7684\u9876\u5c42\u4f7f\u7528\u4e00\u4e2a\u6355\u6349\u5168\u90e8\u5f02\u5e38\u7684\u5757\uff09\u3002\u5373\u4f7f C++ \u4ee3\u7801\u4e0d\u4f1a\u663e\u5f0f\u5730\u629b\u51fa\u4efb\u4f55\u5f02\u5e38\u4e5f\u9700\u8981\u8fd9\u6837\u505a\uff0c\u56e0\u4e3a\u7c7b\u4f3c\u5185\u5b58\u4e0d\u8db3\u7b49\u4e8b\u4ef6\u4ecd\u4f1a\u629b\u51fa\u5f02\u5e38\u3002\u4efb\u4f55\u5f02\u5e38\u90fd\u5fc5\u987b\u88ab\u6355\u6349\u5e76\u4e14\u7528\u9002\u5f53\u7684\u9519\u8bef\u4f20\u56de\u7ed9 C \u63a5\u53e3\u3002\u5982\u679c\u53ef\u80fd\uff0c\u7528 -fno-exceptions \u6765\u7f16\u8bd1 C++ \u4ee5\u5b8c\u5168\u6d88\u706d\u5f02\u5e38\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u4f60\u5fc5\u987b\u5728 C++ \u4ee3\u7801\u4e2d\u68c0\u67e5\u5931\u8d25\uff0c\u4f8b\u5982\u68c0\u67e5new() \u8fd4\u56de\u7684 NULL\u3002

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    • \n
  • \u4ece C++ \u4ee3\u7801\u8c03\u7528\u540e\u7aef\u51fd\u6570\u65f6\uff0c\u5fc5\u987b\u786e\u4fdd C++ \u8c03\u7528\u6808\u4e2d\u4ec5\u5305\u542b\u666e\u901a\u65e7\u5f0f\u6570\u636e\u7ed3\u6784\uff08POD\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u7aef\u9519\u8bef\u4f1a\u89e6\u53d1\u8fdc\u8ddd\u79bb longjmp()\uff0c\u65e0\u6cd5\u6b63\u786e\u5c55\u5f00\u5305\u542b\u975e POD \u5bf9\u8c61\u7684 C++ \u8c03\u7528\u6808\u3002
    • \n
\n
\n

\u603b\u4e4b\uff0c\u6700\u597d\u628a C++ \u4ee3\u7801\u653e\u5728\u4e0e\u540e\u7aef\u4ea4\u4e92\u7684extern C\u51fd\u6570\u4e4b\u540e\uff0c\u5e76\u4e14\u907f\u514d\u5f02\u5e38\u3001\u5185\u5b58\u548c\u8c03\u7528\u6808\u6cc4\u6f0f\u3002

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