{"kind": "plan", "major": "18", "item": {"slug": "subquery-scan", "name": "Subquery Scan", "name_zh": "SubqueryScan", "category": "\u626b\u63cf", "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "aliases": ["Subquery Scan", "SubqueryScan", "T_SubqueryScan"], "content_hash": "c2434a2d92a7a7414f5313ce9e811fa69a6d68071857328890d6409d4e8bdfdc", "versions": {"10": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "cf361acd5eecec1ec2668622daa7e987c28eff8e10f8f10c1072d0f452a67469", "archive_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}], "mechanism": "unclassified", "description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=10", "label": "EXPLAIN"}, {"url": "/docs/10/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/10/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 10.23 source archive", "label": "10.23", "major": "10", "channel": "historical", "revision": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9", "source_url": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": 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"\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "10", "text_hash": "645f510f62cb7b2687492c426b08e01b2a85c0f7d720e9076320632e8ff8fdfd", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/10/performance-tips.html#USING-EXPLAIN", "anchor": "USING-EXPLAIN", "locale": "zh-Hans", "version": "10", "build_id": 63, "page_key": "performance-tips.html", "extraction": "concept-introduction", "source_hash": "04aacb3e491b4aeabbfc54a60ddedcc5fafcc469c0823a375c35a83ec42575c6", "fragment_sha256": "82af09517c7be979ac518f6bede1cb5e44f328ebf207cc6b25aa2313dff5f7a6", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "snapshot:sha256:62997ea80516ad012fbf6359de33f3b016b54c47e2df76e75606116b4baaf8e5", "translated_from_revision": null}, "body_sha256": "f482cbedbdd6fdf4f076d2679098b8052c36edde350d19ef7f2afe123f7b2c9a", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p> <span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"xref\" href=\"/zh/docs/10/sql-explain.html\"><span class=\"refentrytitle\">EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/10/performance-tips.html#USING-EXPLAIN\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "10", "link_map": {"/zh/docs/10/sql-explain.html": "/docs/10/sql-explain.html", "/zh/docs/10/performance-tips.html#USING-EXPLAIN": "/docs/10/performance-tips.html#USING-EXPLAIN"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p> <span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/10/sql-explain.html\" rel=\"nofollow\"><span>EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/10/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "41849d2636d75bbfe14a1c43ba6f6d847a298551de42277c0bbef6f89c3b1bca", "content_hash": "645f510f62cb7b2687492c426b08e01b2a85c0f7d720e9076320632e8ff8fdfd", "source_database": "center", "source_revision": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/10/description/0": "Scans the output of a subquery plan.", "/versions/10/facts/0/label": "Core node tag", "/versions/10/facts/1/label": "Structured EXPLAIN Node Type", "/versions/10/facts/2/label": "Inputs", "/versions/10/facts/2/value": "A subquery child plan", "/versions/10/facts/3/label": "Output", "/versions/10/facts/3/value": "Subquery result tuples", "/versions/10/facts/4/label": "Executor initializer", "/versions/10/facts/5/label": "Memory mechanism", "/versions/10/tables/0/title": "EXPLAIN labels in this source build", "/versions/10/related/1/label": "Using EXPLAIN", "/versions/10/related/2/label": "Parallel plans", "/versions/10/sections/0/title": "EXPLAIN names and attributes", "/versions/10/sections/1/title": "Memory and temporary storage", "/versions/10/sections/2/title": "Parallel execution and instrumentation", "/versions/10/sections/3/title": "Executor implementation notes", "/versions/10/sections/4/title": "EXPLAIN identity in core source", "/versions/10/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/10/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/10/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/10/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/10/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/10/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/10/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/10/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/10/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/10/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/10/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/10/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/10/tables/0/columns/0/label": "Text-format label", "/versions/10/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "6aa2a5f7a5f9f2dd2cb88d208e66368a3b897e6a47f34a96bdab7f4a5fae1715", "canonical_center_text_hash": "645f510f62cb7b2687492c426b08e01b2a85c0f7d720e9076320632e8ff8fdfd"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", 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Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p> <span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/10/sql-explain.html\" rel=\"nofollow\"><span>EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> 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"paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "11", "text_hash": "36ef296bce575c207ec11bb6ceb8ac7d6037497dd785e51f0c23ae9990d462b6", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/11/performance-tips.html#USING-EXPLAIN", "anchor": "USING-EXPLAIN", "locale": "zh-Hans", "version": "11", "build_id": 64, "page_key": "performance-tips.html", "extraction": "concept-introduction", "source_hash": "617a30102327f61276ba77fb034f4bf1bbb677d91d4eb5507dc14d740e6394c9", "fragment_sha256": "a7b71780192bea8bfc169883aae459f6d32a71fe928f60388479827c9c8b54bc", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "snapshot:sha256:ef5c7bc074acae9795db16e6b7482aea3b222bd4bcce0f76831332b97a21e8a1", "translated_from_revision": null}, "body_sha256": "bc93eee154522a66929c8d399ee4230d5a2fc13073b32fdd24be4dca8e62b11e", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"xref\" href=\"/zh/docs/11/sql-explain.html\"><span class=\"refentrytitle\">EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/11/performance-tips.html#USING-EXPLAIN\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "11", "link_map": {"/zh/docs/11/sql-explain.html": "/docs/11/sql-explain.html", "/zh/docs/11/performance-tips.html#USING-EXPLAIN": "/docs/11/performance-tips.html#USING-EXPLAIN"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/11/sql-explain.html\" rel=\"nofollow\"><span>EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/11/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "a1799af19b3a68b0fbc24cab05d6cc51355b75024f05af3b6a385746b2f77d4e", "content_hash": "36ef296bce575c207ec11bb6ceb8ac7d6037497dd785e51f0c23ae9990d462b6", "source_database": "center", "source_revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/11/description/0": "Scans the output of a subquery plan.", "/versions/11/facts/0/label": "Core node tag", "/versions/11/facts/1/label": "Structured EXPLAIN Node Type", "/versions/11/facts/2/label": "Inputs", "/versions/11/facts/2/value": "A subquery child plan", "/versions/11/facts/3/label": "Output", "/versions/11/facts/3/value": "Subquery result tuples", "/versions/11/facts/4/label": "Executor initializer", "/versions/11/facts/5/label": "Memory mechanism", "/versions/11/tables/0/title": "EXPLAIN labels in this source build", "/versions/11/related/1/label": "Using EXPLAIN", "/versions/11/related/2/label": "Parallel plans", "/versions/11/sections/0/title": "EXPLAIN names and attributes", "/versions/11/sections/1/title": "Memory and temporary storage", "/versions/11/sections/2/title": "Parallel execution and instrumentation", "/versions/11/sections/3/title": "Executor implementation notes", "/versions/11/sections/4/title": "EXPLAIN identity in core source", "/versions/11/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/11/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/11/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/11/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/11/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/11/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/11/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/11/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/11/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/11/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/11/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/11/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/11/tables/0/columns/0/label": "Text-format label", "/versions/11/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "7ac8d466049bfb7202a148940b228316a31e93e5482bd63d3be5e44a592caa94", "canonical_center_text_hash": "36ef296bce575c207ec11bb6ceb8ac7d6037497dd785e51f0c23ae9990d462b6"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/11/sql-explain.html\" rel=\"nofollow\"><span>EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> 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Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=12", "label": "EXPLAIN"}, {"url": "/docs/12/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/12/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 12.22 source archive", "label": "12.22", "major": "12", "channel": "historical", "revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b", "source_url": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": 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"\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "12", "text_hash": "c2a4a2b8e3aa911b3bd906dd7ffd626f196ebd1ce9707bad9b6fcdf6bdc50af6", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/12/performance-tips.html#USING-EXPLAIN", "anchor": "USING-EXPLAIN", "locale": "zh-Hans", "version": "12", "build_id": 65, "page_key": "performance-tips.html", "extraction": "concept-introduction", "source_hash": "773efea8d76bcea57eb449ceb506a51025a4125ceaa9b765a1039e558f5cfe98", "fragment_sha256": "5563b70cc4f15175ea74a689b7145d309617eefbe2ea27e4fce422e01369eff6", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "snapshot:sha256:86d2ff781f93e1de17122ebc514d5e64fcb63fed15941f496d7e146c6dcc7a49", "translated_from_revision": null}, "body_sha256": "270f999b38b9a4e7b28ee77150a220314729531ae87291c2d05236987266e5a4", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"xref\" href=\"/zh/docs/12/sql-explain.html\"><span class=\"refentrytitle\">EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/12/performance-tips.html#USING-EXPLAIN\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "12", "link_map": {"/zh/docs/12/sql-explain.html": "/docs/12/sql-explain.html", "/zh/docs/12/performance-tips.html#USING-EXPLAIN": "/docs/12/performance-tips.html#USING-EXPLAIN"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/12/sql-explain.html\" rel=\"nofollow\"><span>EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/12/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "467a52bff9bb363147632497c5442f9408c741abd02b1aa4b2415fab1e772281", "content_hash": "c2a4a2b8e3aa911b3bd906dd7ffd626f196ebd1ce9707bad9b6fcdf6bdc50af6", "source_database": "center", "source_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/12/description/0": "Scans the output of a subquery plan.", "/versions/12/facts/0/label": "Core node tag", "/versions/12/facts/1/label": "Structured EXPLAIN Node Type", "/versions/12/facts/2/label": "Inputs", "/versions/12/facts/2/value": "A subquery child plan", "/versions/12/facts/3/label": "Output", "/versions/12/facts/3/value": "Subquery result tuples", "/versions/12/facts/4/label": "Executor initializer", "/versions/12/facts/5/label": "Memory mechanism", "/versions/12/tables/0/title": "EXPLAIN labels in this source build", "/versions/12/related/1/label": "Using EXPLAIN", "/versions/12/related/2/label": "Parallel plans", "/versions/12/sections/0/title": "EXPLAIN names and attributes", "/versions/12/sections/1/title": "Memory and temporary storage", "/versions/12/sections/2/title": "Parallel execution and instrumentation", "/versions/12/sections/3/title": "Executor implementation notes", "/versions/12/sections/4/title": "EXPLAIN identity in core source", "/versions/12/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/12/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/12/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/12/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/12/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/12/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/12/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/12/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/12/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/12/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/12/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/12/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/12/tables/0/columns/0/label": "Text-format label", "/versions/12/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "d96fb305a38c02573784855cec1537aedd515334b8e0025b7153168ac833a784", "canonical_center_text_hash": "c2a4a2b8e3aa911b3bd906dd7ffd626f196ebd1ce9707bad9b6fcdf6bdc50af6"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/12/sql-explain.html\" rel=\"nofollow\"><span>EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/12/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "13": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v13.23/postgresql-13.23.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "3eb09b2b542681ad211e5f7feb045d498278f61f8614769cf3faae40720ddb7e", "archive_sha256": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}], "mechanism": "unclassified", "description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=13", "label": "EXPLAIN"}, {"url": "/docs/13/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/13/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 13.23 source archive", "label": "13.23", "major": "13", "channel": "historical", "revision": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6", "source_url": "https://ftp.postgresql.org/pub/source/v13.23/postgresql-13.23.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": 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"authored-translation-of-reviewed-guidance", "source_facts_revision": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"xref\" href=\"/zh/docs/13/sql-explain.html\"><span class=\"refentrytitle\">EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/13/performance-tips.html#USING-EXPLAIN\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "13", "link_map": {"/zh/docs/13/sql-explain.html": "/docs/13/sql-explain.html", "/zh/docs/13/performance-tips.html#USING-EXPLAIN": "/docs/13/performance-tips.html#USING-EXPLAIN"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/13/sql-explain.html\" rel=\"nofollow\"><span>EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/13/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "6086333d751b8854983473aa7b56d1eed0fdebb08b61060304ed29b0236cad39", "content_hash": "12ca8f10b4947a53999eaae67a1147b830de25e659901dc4e7bc8f3fb263bee0", "source_database": "center", "source_revision": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/13/description/0": "Scans the output of a subquery plan.", "/versions/13/facts/0/label": "Core node tag", "/versions/13/facts/1/label": "Structured EXPLAIN Node Type", "/versions/13/facts/2/label": "Inputs", "/versions/13/facts/2/value": "A subquery child plan", "/versions/13/facts/3/label": "Output", "/versions/13/facts/3/value": "Subquery result tuples", "/versions/13/facts/4/label": "Executor initializer", "/versions/13/facts/5/label": "Memory mechanism", "/versions/13/tables/0/title": "EXPLAIN labels in this source build", "/versions/13/related/1/label": "Using EXPLAIN", "/versions/13/related/2/label": "Parallel plans", "/versions/13/sections/0/title": "EXPLAIN names and attributes", "/versions/13/sections/1/title": "Memory and temporary storage", "/versions/13/sections/2/title": "Parallel execution and instrumentation", "/versions/13/sections/3/title": "Executor implementation notes", "/versions/13/sections/4/title": "EXPLAIN identity in core source", "/versions/13/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/13/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/13/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/13/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/13/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/13/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/13/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/13/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/13/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/13/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/13/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/13/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/13/tables/0/columns/0/label": "Text-format label", "/versions/13/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "6b17e80d277a3beed196e4060f6778c3e01dc5205b4a12c8eb12bead50705703", "canonical_center_text_hash": "12ca8f10b4947a53999eaae67a1147b830de25e659901dc4e7bc8f3fb263bee0"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/13/sql-explain.html\" rel=\"nofollow\"><span>EXPLAIN</span></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/13/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "14": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "a97d270f24122ea18316fa70621fb7401286171a6ddac0869d87262f0f110bb0", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}], "mechanism": "unclassified", "description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=14", "label": "EXPLAIN"}, {"url": "/docs/14/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/14/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 14.24 source archive", "label": "14.24", "major": "14", "channel": "stable", "revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897", "source_url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "line": 1252, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1252", "sha256": "e091be4e2a083b8dea39ccd09beedede22c1716ef974da66c214a44f48be8c41", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, {"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "line": 249, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:249", "sha256": "72da1c5ad457f1d92a39ab73531701794df858419e3b89d6e6cb7079634e68fa", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, {"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "a97d270f24122ea18316fa70621fb7401286171a6ddac0869d87262f0f110bb0", "archive_sha256": 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"git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:87e6aa4fd6e1ec85c5f4a6de4f5647cfd9e5de734ca2c266d32b6d6192c662ef", "translated_from_revision": null}, "body_sha256": "8928ad333cadea8d0397b204da216145bd81a942f676222493564dd54ee1b056", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_SubqueryScan", "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "14", "text_hash": "e8eee3ab93d26b529b8d9b5d5c22b1a51aadfbb1ef1b4e67f58551c49bb87723", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/14/performance-tips.html#USING-EXPLAIN", "anchor": "USING-EXPLAIN", "locale": "zh-Hans", "version": "14", "build_id": 99, "page_key": "performance-tips.html", "extraction": "concept-introduction", "source_hash": "62cadce9a200c7891b3bbf04fc22c8dc17b4525aec0d020a074310592666f6d4", "fragment_sha256": "44f0e04fca33c2837461b83f68b9337a6abf37b979c0097630f9ab322fb3c567", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:87e6aa4fd6e1ec85c5f4a6de4f5647cfd9e5de734ca2c266d32b6d6192c662ef", "translated_from_revision": null}, "body_sha256": "8928ad333cadea8d0397b204da216145bd81a942f676222493564dd54ee1b056", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"link\" href=\"/zh/docs/14/sql-explain.html\"><code class=\"command\">EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/14/performance-tips.html#USING-EXPLAIN\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "14", "link_map": {"/zh/docs/14/sql-explain.html": "/docs/14/sql-explain.html", "/zh/docs/14/performance-tips.html#USING-EXPLAIN": "/docs/14/performance-tips.html#USING-EXPLAIN"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/14/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/14/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "66e2258e12e2b696d15220887026113b157ad2bcb9ff4aa61deadc6a4411de67", "content_hash": "e8eee3ab93d26b529b8d9b5d5c22b1a51aadfbb1ef1b4e67f58551c49bb87723", "source_database": "center", "source_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/14/description/0": "Scans the output of a subquery plan.", "/versions/14/facts/0/label": "Core node tag", "/versions/14/facts/1/label": "Structured EXPLAIN Node Type", "/versions/14/facts/2/label": "Inputs", "/versions/14/facts/2/value": "A subquery child plan", "/versions/14/facts/3/label": "Output", "/versions/14/facts/3/value": "Subquery result tuples", "/versions/14/facts/4/label": "Executor initializer", "/versions/14/facts/5/label": "Memory mechanism", "/versions/14/tables/0/title": "EXPLAIN labels in this source build", "/versions/14/related/1/label": "Using EXPLAIN", "/versions/14/related/2/label": "Parallel plans", "/versions/14/sections/0/title": "EXPLAIN names and attributes", "/versions/14/sections/1/title": "Memory and temporary storage", "/versions/14/sections/2/title": "Parallel execution and instrumentation", "/versions/14/sections/3/title": "Executor implementation notes", "/versions/14/sections/4/title": "EXPLAIN identity in core source", "/versions/14/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/14/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/14/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/14/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/14/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/14/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/14/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/14/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/14/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/14/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/14/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/14/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/14/tables/0/columns/0/label": "Text-format label", "/versions/14/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "70d5cd6b78138eb88c475d29166123159d551680b05cd347aea4faeada9a8c60", "canonical_center_text_hash": "e8eee3ab93d26b529b8d9b5d5c22b1a51aadfbb1ef1b4e67f58551c49bb87723"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel", "Async"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/14/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> 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\u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "15", "text_hash": "507dd0b33d314efc9788116ff93c52939a6614b54b24f27f680777bbaaf33227", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/15/performance-tips.html#USING-EXPLAIN", "anchor": "USING-EXPLAIN", "locale": "zh-Hans", "version": "15", "build_id": 101, "page_key": "performance-tips.html", "extraction": "concept-introduction", "source_hash": "d842974e11d60f39bee19269d456c1cf6a01bc6c2c3ac27d8d1e7966ef5f46b9", "fragment_sha256": "16561716621b0c2403eaa78c0cd62211754eaec8fd5716f685f693e1deb3a07b", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:6bce1a2df9170cb1146a1411c5547190856638221a6539e618ee1016c9f493ad", "translated_from_revision": null}, "body_sha256": "df659e7780f03a421410761c0fc1fcb8c0de9c604f4d4310b784f07a9c392870", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"link\" href=\"/zh/docs/15/sql-explain.html\"><code class=\"command\">EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/15/performance-tips.html#USING-EXPLAIN\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "15", "link_map": {"/zh/docs/15/sql-explain.html": "/docs/15/sql-explain.html", "/zh/docs/15/performance-tips.html#USING-EXPLAIN": "/docs/15/performance-tips.html#USING-EXPLAIN"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/15/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/15/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "80c624ab5bbecdcd40ed1e91431a477145f0a611a14f9bd5ded291679e52fbcf", "content_hash": "507dd0b33d314efc9788116ff93c52939a6614b54b24f27f680777bbaaf33227", "source_database": "center", "source_revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/15/description/0": "Scans the output of a subquery plan.", "/versions/15/facts/0/label": "Core node tag", "/versions/15/facts/1/label": "Structured EXPLAIN Node Type", "/versions/15/facts/2/label": "Inputs", "/versions/15/facts/2/value": "A subquery child plan", "/versions/15/facts/3/label": "Output", "/versions/15/facts/3/value": "Subquery result tuples", "/versions/15/facts/4/label": "Executor initializer", "/versions/15/facts/5/label": "Memory mechanism", "/versions/15/tables/0/title": "EXPLAIN labels in this source build", "/versions/15/related/1/label": "Using EXPLAIN", "/versions/15/related/2/label": "Parallel plans", "/versions/15/sections/0/title": "EXPLAIN names and attributes", "/versions/15/sections/1/title": "Memory and temporary storage", "/versions/15/sections/2/title": "Parallel execution and instrumentation", "/versions/15/sections/3/title": "Executor implementation notes", "/versions/15/sections/4/title": "EXPLAIN identity in core source", "/versions/15/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/15/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/15/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/15/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/15/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/15/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/15/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/15/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/15/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/15/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/15/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/15/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/15/tables/0/columns/0/label": "Text-format label", "/versions/15/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "9841b22c27ef593c9f81d5a96405245bc42cef4d5740f1d0d9d219c9bdce36a3", "canonical_center_text_hash": "507dd0b33d314efc9788116ff93c52939a6614b54b24f27f680777bbaaf33227"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel", "Async"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/15/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/15/performance-tips.html#USING-EXPLAIN\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "16": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "19a3c96d04960ac87ca0c52aea31493ab9ae4590a2578bec2dd0fb6795d640ba", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}], "mechanism": "unclassified", "description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=16", "label": "EXPLAIN"}, {"url": "/docs/16/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/16/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 16.15 source archive", "label": "16.15", "major": "16", "channel": "stable", "revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed", "source_url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "line": 1288, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1288", "sha256": "8e017f0116dbea471339b40c37a667cc9f95039e7e0329c783e5e8ce194de7e1", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, {"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "line": 249, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:249", "sha256": "e48c08e555f8cb4e4bb43df516c4b8906ce9bc374b2a745d98a1fc8c22cc5099", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, {"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "19a3c96d04960ac87ca0c52aea31493ab9ae4590a2578bec2dd0fb6795d640ba", "archive_sha256": 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"git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:80579a071736780f9c4022bb5148e1fb1256f1a33591306af67816e9e9bf3a9b", "translated_from_revision": null}, "body_sha256": "2e499be7d74c9ea3a0f70f45f737ecbe075de65b3bddf35939504a610ad07383", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_SubqueryScan", "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", 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\u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "16", "text_hash": "56af1f180b0e93c1878078854bc87286990716003c941edd3b18a30fce2910b2", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": 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"translated_from_revision": null}, "body_sha256": "2e499be7d74c9ea3a0f70f45f737ecbe075de65b3bddf35939504a610ad07383", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"link\" href=\"/zh/docs/16/sql-explain.html\"><code class=\"command\">EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/16/using-explain.html\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "16", "link_map": {"/zh/docs/16/sql-explain.html": "/docs/16/sql-explain.html", "/zh/docs/16/using-explain.html": "/docs/16/using-explain.html"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/16/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/16/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "062a3840423ed7d27c366ee8fc64ca1f5f57862c9d666d0dd827b5af4a0f3d1b", "content_hash": "56af1f180b0e93c1878078854bc87286990716003c941edd3b18a30fce2910b2", "source_database": "center", "source_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/16/description/0": "Scans the output of a subquery plan.", "/versions/16/facts/0/label": "Core node tag", "/versions/16/facts/1/label": "Structured EXPLAIN Node Type", "/versions/16/facts/2/label": "Inputs", "/versions/16/facts/2/value": "A subquery child plan", "/versions/16/facts/3/label": "Output", "/versions/16/facts/3/value": "Subquery result tuples", "/versions/16/facts/4/label": "Executor initializer", "/versions/16/facts/5/label": "Memory mechanism", "/versions/16/tables/0/title": "EXPLAIN labels in this source build", "/versions/16/related/1/label": "Using EXPLAIN", "/versions/16/related/2/label": "Parallel plans", "/versions/16/sections/0/title": "EXPLAIN names and attributes", "/versions/16/sections/1/title": "Memory and temporary storage", "/versions/16/sections/2/title": "Parallel execution and instrumentation", "/versions/16/sections/3/title": "Executor implementation notes", "/versions/16/sections/4/title": "EXPLAIN identity in core source", "/versions/16/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/16/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/16/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/16/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/16/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/16/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/16/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/16/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/16/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/16/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/16/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/16/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/16/tables/0/columns/0/label": "Text-format label", "/versions/16/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "8393fd4c91e94d09906ae4543f9bb91c1511b51021b6fdcd9ef76e6b2d3eba6f", "canonical_center_text_hash": "56af1f180b0e93c1878078854bc87286990716003c941edd3b18a30fce2910b2"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel", "Async"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/16/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f 9.3 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/16/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "17": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "3ce294038952ff3960bbfb30d1f2cfa89c04b3bc5014587a1f58107f3d629634", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}], "mechanism": "unclassified", "description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=17", "label": "EXPLAIN"}, {"url": "/docs/17/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/17/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 17.11 source archive", "label": "17.11", "major": "17", "channel": "stable", "revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979", "source_url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "line": 1477, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1477", "sha256": "741251b1a3b6d269a52a673d42eb63b02e13a5872db7b359b137086ab21b63c8", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, {"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "line": 249, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:249", "sha256": "a77576e158b94cb01fa8c5174ba133004eabdd727660323f8afc66c8d2e757b8", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, {"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "3ce294038952ff3960bbfb30d1f2cfa89c04b3bc5014587a1f58107f3d629634", "archive_sha256": 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"git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:7340767258d21c21b36f373f1fff6bab2be18e0daca13a865129db6105c09efd", "translated_from_revision": null}, "body_sha256": "712df72fcc372199c78c2fc4d54ed75a4f202954c81c0dbf2644d288ddd25e97", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_SubqueryScan", "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "17", "text_hash": "5f45b4225edb47e5dc7fdbf138b55aa2423a9b6889b9223036bdecef35554a0f", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/17/using-explain.html", "anchor": "", "locale": "zh-Hans", "version": "17", "build_id": 105, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "b1252952c6d796f5e38c223b74ff667f2d19d677dcf85fe5269b782b830e5013", "fragment_sha256": "8f5243c368dfae57e826af49b7461d37d7f4d97207bd5f540aebe6b10a61f883", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:7340767258d21c21b36f373f1fff6bab2be18e0daca13a865129db6105c09efd", "translated_from_revision": null}, "body_sha256": "712df72fcc372199c78c2fc4d54ed75a4f202954c81c0dbf2644d288ddd25e97", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"link\" href=\"/zh/docs/17/sql-explain.html\"><code class=\"command\">EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v17 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/17/using-explain.html\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "17", "link_map": {"/zh/docs/17/sql-explain.html": "/docs/17/sql-explain.html", "/zh/docs/17/using-explain.html": "/docs/17/using-explain.html"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/17/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v17 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/17/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "8d007b6e868afea5fe7efbfba99492b1ca9470a3389973c9319395b3a5e1a65e", "content_hash": "5f45b4225edb47e5dc7fdbf138b55aa2423a9b6889b9223036bdecef35554a0f", "source_database": "center", "source_revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/17/description/0": "Scans the output of a subquery plan.", "/versions/17/facts/0/label": "Core node tag", "/versions/17/facts/1/label": "Structured EXPLAIN Node Type", "/versions/17/facts/2/label": "Inputs", "/versions/17/facts/2/value": "A subquery child plan", "/versions/17/facts/3/label": "Output", "/versions/17/facts/3/value": "Subquery result tuples", "/versions/17/facts/4/label": "Executor initializer", "/versions/17/facts/5/label": "Memory mechanism", "/versions/17/tables/0/title": "EXPLAIN labels in this source build", "/versions/17/related/1/label": "Using EXPLAIN", "/versions/17/related/2/label": "Parallel plans", "/versions/17/sections/0/title": "EXPLAIN names and attributes", "/versions/17/sections/1/title": "Memory and temporary storage", "/versions/17/sections/2/title": "Parallel execution and instrumentation", "/versions/17/sections/3/title": "Executor implementation notes", "/versions/17/sections/4/title": "EXPLAIN identity in core source", "/versions/17/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/17/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/17/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/17/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/17/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/17/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/17/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/17/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/17/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/17/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/17/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/17/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/17/tables/0/columns/0/label": "Text-format label", "/versions/17/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "c5fa86a414617898c5e4e61a10956ca1efc3bdd84b8abe2a8de420ba380a3ee0", "canonical_center_text_hash": "5f45b4225edb47e5dc7fdbf138b55aa2423a9b6889b9223036bdecef35554a0f"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel", "Async"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/17/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v17 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> 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Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=18", "label": "EXPLAIN"}, {"url": "/docs/18/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/18/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 18.6 source archive", "label": "18.6", "major": "18", "channel": "stable", "revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f", "source_url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": 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\u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "18", "text_hash": "cbf05e93c65e58ee4a493331796098a26a165c5e4cd6bd4cfe03c6f57db95840", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/18/using-explain.html", "anchor": "", "locale": "zh-Hans", "version": "18", "build_id": 107, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "d2f749744b3ac5aa2eb0154f295e8163903cd20fcc130c74c6172cdf2ae3a9df", "fragment_sha256": "15fbdf84b8f499253ade4f4a5841de138619a9933b93cc241d431dbe922fa40c", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b", "translated_from_revision": null}, "body_sha256": "bbd6669c81029c18d1423d81f36ea2f0637abafd463480c2f676c9ec6fe6fd4e", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"link\" href=\"/zh/docs/18/sql-explain.html\"><code class=\"command\">EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "18", "link_map": {"/zh/docs/18/sql-explain.html": "/docs/18/sql-explain.html", "/zh/docs/18/using-explain.html": "/docs/18/using-explain.html"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/18/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "a307beecc8c4bd0f009fe669db7f60dab07420db237eefe0dcb42036ec86d41d", "content_hash": "cbf05e93c65e58ee4a493331796098a26a165c5e4cd6bd4cfe03c6f57db95840", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/18/description/0": "Scans the output of a subquery plan.", "/versions/18/facts/0/label": "Core node tag", "/versions/18/facts/1/label": "Structured EXPLAIN Node Type", "/versions/18/facts/2/label": "Inputs", "/versions/18/facts/2/value": "A subquery child plan", "/versions/18/facts/3/label": "Output", "/versions/18/facts/3/value": "Subquery result tuples", "/versions/18/facts/4/label": "Executor initializer", "/versions/18/facts/5/label": "Memory mechanism", "/versions/18/tables/0/title": "EXPLAIN labels in this source build", "/versions/18/related/1/label": "Using EXPLAIN", "/versions/18/related/2/label": "Parallel plans", "/versions/18/sections/0/title": "EXPLAIN names and attributes", "/versions/18/sections/1/title": "Memory and temporary storage", "/versions/18/sections/2/title": "Parallel execution and instrumentation", "/versions/18/sections/3/title": "Executor implementation notes", "/versions/18/sections/4/title": "EXPLAIN identity in core source", "/versions/18/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/18/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/18/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/18/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/18/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/18/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/18/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/18/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/18/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/18/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/18/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/18/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/18/tables/0/columns/0/label": "Text-format label", "/versions/18/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "69301e70f0200d5845e679ff940a2d05cc2ab7e7c6ac58394fa39691e17c321e", "canonical_center_text_hash": "cbf05e93c65e58ee4a493331796098a26a165c5e4cd6bd4cfe03c6f57db95840"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel", "Async"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/18/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "center_zh_rendered": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/docs/18/sql-explain.html\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/docs/18/using-explain.html\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "19": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v19beta4/postgresql-19beta4.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "d1b51e26a2a3d88556a1267b58740ae047d1ff403c57e8f5ee53d7f35376f37c", "archive_sha256": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}], "mechanism": "unclassified", "description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=19", "label": "EXPLAIN"}, {"url": "/docs/19/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/19/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 19rc1 source archive", "label": "19rc1", "major": "19", "channel": "preview", "revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701", "source_url": "https://ftp.postgresql.org/pub/source/v19rc1/postgresql-19rc1.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v19rc1/postgresql-19rc1.tar.bz2", "line": 1474, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1474", "sha256": "8b115b1c194a4b54ae630209a741e293b1df49a9052f10b2de9ca092a48998e3", "archive_sha256": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, {"url": "https://ftp.postgresql.org/pub/source/v19rc1/postgresql-19rc1.tar.bz2", "line": 249, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:249", "sha256": "5e39b2037bed672da55104229ecc32da5abde44c26bcad01479edcfa044d09ed", "archive_sha256": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, {"url": "https://ftp.postgresql.org/pub/source/v19rc1/postgresql-19rc1.tar.bz2", "path": "src/backend/executor/nodeSubqueryscan.c", "label": "src/backend/executor/nodeSubqueryscan.c", "sha256": "d1b51e26a2a3d88556a1267b58740ae047d1ff403c57e8f5ee53d7f35376f37c", "archive_sha256": 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"git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:65fda1f1b62a89992b84014c9157e61b67dbe8190e93945826efec668fad038c", "translated_from_revision": "sha256:af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "body_sha256": "8873ad2479d530ddf3fe2c19f8a6971eaee1b47baace9bdd74fa92decd7cc2c0", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_SubqueryScan", "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "19", "text_hash": "94a9f466040117640e27b6727f3d8befa86a9c826ac60439143695b7893e4926", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/19/using-explain.html", "anchor": "", "locale": "zh-Hans", "version": "19", "build_id": 109, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "9bbb1ef5924e4788a3dc2642828383c67ab8651fb6b0e45924c454f095b0ff47", "fragment_sha256": "1ceb32499da15c4bcec0644765b693adbc1991296745e00460ce28d06d701ef3", "source_revision": "sha256:af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:65fda1f1b62a89992b84014c9157e61b67dbe8190e93945826efec668fad038c", "translated_from_revision": "sha256:af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "body_sha256": "8873ad2479d530ddf3fe2c19f8a6971eaee1b47baace9bdd74fa92decd7cc2c0", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"link\" href=\"/zh/docs/19/sql-explain.html\"><code class=\"command\">EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/19/using-explain.html\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "19", "link_map": {"/zh/docs/19/sql-explain.html": "/docs/19/sql-explain.html", "/zh/docs/19/using-explain.html": "/docs/19/using-explain.html"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/19/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/19/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "b1409b11955cbdedf2bbc56c61ff8020e7768dc5ae1185605c734c0e66ecd952", "content_hash": "94a9f466040117640e27b6727f3d8befa86a9c826ac60439143695b7893e4926", "source_database": "center", "source_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/19/description/0": "Scans the output of a subquery plan.", "/versions/19/facts/0/label": "Core node tag", "/versions/19/facts/1/label": "Structured EXPLAIN Node Type", "/versions/19/facts/2/label": "Inputs", "/versions/19/facts/2/value": "A subquery child plan", "/versions/19/facts/3/label": "Output", "/versions/19/facts/3/value": "Subquery result tuples", "/versions/19/facts/4/label": "Executor initializer", "/versions/19/facts/5/label": "Memory mechanism", "/versions/19/tables/0/title": "EXPLAIN labels in this source build", "/versions/19/related/1/label": "Using EXPLAIN", "/versions/19/related/2/label": "Parallel plans", "/versions/19/sections/0/title": "EXPLAIN names and attributes", "/versions/19/sections/1/title": "Memory and temporary storage", "/versions/19/sections/2/title": "Parallel execution and instrumentation", "/versions/19/sections/3/title": "Executor implementation notes", "/versions/19/sections/4/title": "EXPLAIN identity in core source", "/versions/19/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/19/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/19/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/19/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/19/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/19/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/19/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/19/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/19/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/19/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/19/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/19/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. 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"git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:98c980963b401d40bd50df72b909e7523e3148b8fdb48edd897de2efb67e5235", "translated_from_revision": "sha256:49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "body_sha256": "0cf6773e75a55231a43c09d0f8e90ff5f07b4d2e836a232bea81a9cc55e63520", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_SubqueryScan", "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "20", "text_hash": "26b63d2e59a69a3217fe72053737021a4cb6bab115dc4bb1beb7b84ea00e3e36", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/devel/using-explain.html", "anchor": "", "locale": "zh-Hans", "version": "20", "build_id": 111, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "436517563e51b6d851ef143e70d01f5f68fe0a01e00a0d507e7bd79d7570aa25", "fragment_sha256": "f2d2c226e0479b8d931accead1f2cf7c1b8646afa24d8025ea5d5bcab837f779", "source_revision": "sha256:49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:98c980963b401d40bd50df72b909e7523e3148b8fdb48edd897de2efb67e5235", "translated_from_revision": "sha256:49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "body_sha256": "0cf6773e75a55231a43c09d0f8e90ff5f07b4d2e836a232bea81a9cc55e63520", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"link\" href=\"/zh/docs/devel/sql-explain.html\"><code class=\"command\">EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/devel/using-explain.html\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "20", "link_map": {"/zh/docs/devel/sql-explain.html": "/docs/devel/sql-explain.html", "/zh/docs/devel/using-explain.html": "/docs/devel/using-explain.html"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/devel/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/devel/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "b0899e37b0edbfda93ccc36720d71699009e8a1c45df57691e08b982330ce16f", "content_hash": "26b63d2e59a69a3217fe72053737021a4cb6bab115dc4bb1beb7b84ea00e3e36", "source_database": "center", "source_revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/summary": "Scans the output of a subquery plan.", "/category": "Scan", "/versions/20/description/0": "Scans the output of a subquery plan.", "/versions/20/facts/0/label": "Core node tag", "/versions/20/facts/1/label": "Structured EXPLAIN Node Type", "/versions/20/facts/2/label": "Inputs", "/versions/20/facts/2/value": "A subquery child plan", "/versions/20/facts/3/label": "Output", "/versions/20/facts/3/value": "Subquery result tuples", "/versions/20/facts/4/label": "Executor initializer", "/versions/20/facts/5/label": "Memory mechanism", "/versions/20/tables/0/title": "EXPLAIN labels in this source build", "/versions/20/related/1/label": "Using EXPLAIN", "/versions/20/related/2/label": "Parallel plans", "/versions/20/sections/0/title": "EXPLAIN names and attributes", "/versions/20/sections/1/title": "Memory and temporary storage", "/versions/20/sections/2/title": "Parallel execution and instrumentation", "/versions/20/sections/3/title": "Executor implementation notes", "/versions/20/sections/4/title": "EXPLAIN identity in core source", "/versions/20/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/20/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/20/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/20/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/20/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/20/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/20/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/20/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/20/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/20/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/20/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/20/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/20/tables/0/columns/0/label": "Text-format label", "/versions/20/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "798390408590bd819587132c2fc7d4200ebb2d8b0aa9dd80bfcb8b829880411f", "canonical_center_text_hash": "26b63d2e59a69a3217fe72053737021a4cb6bab115dc4bb1beb7b84ea00e3e36"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel", "Async"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/devel/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/devel/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "source_revalidation": {"kind": "static-same-version-source-and-manual-replay", "audit": "wiki-audit-20261023", "runtime_rerun": false, "compared_fields": "entity membership and source-derived facts; 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Inspect the same-build implementation and its expressions or provider.", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=18", "label": "EXPLAIN"}, {"url": "/docs/18/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/18/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 18.6 source archive", "label": "18.6", "major": "18", "channel": "stable", "revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f", "source_url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": 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\u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "SubqueryScan", "locale": "zh-Hans", "source": {"key": "subquery-scan", "locale": "zh-Hans", "version": "18", "text_hash": "cbf05e93c65e58ee4a493331796098a26a165c5e4cd6bd4cfe03c6f57db95840", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_SubqueryScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Subquery Scan"}, {"label": "\u8f93\u5165", "value": "\u5b50\u67e5\u8be2\u7684\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u5b50\u67e5\u8be2\u7ed3\u679c\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitSubqueryScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/18/using-explain.html", "anchor": "", "locale": "zh-Hans", "version": "18", "build_id": 107, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "d2f749744b3ac5aa2eb0154f295e8163903cd20fcc130c74c6172cdf2ae3a9df", "fragment_sha256": "15fbdf84b8f499253ade4f4a5841de138619a9933b93cc241d431dbe922fa40c", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b", "translated_from_revision": null}, "body_sha256": "bbd6669c81029c18d1423d81f36ea2f0637abafd463480c2f676c9ec6fe6fd4e", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sections": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span class=\"productname\">PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em class=\"firstterm\">\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em class=\"firstterm\">\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a class=\"link\" href=\"/zh/docs/18/sql-explain.html\"><code class=\"command\">EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code class=\"command\">VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code class=\"command\">ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code class=\"command\">EXPLAIN</code> \u9ed8\u8ba4\u7684<span class=\"quote\">\u201c<span class=\"quote\">text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code class=\"command\">EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "summary": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "version": "18", "link_map": {"/zh/docs/18/sql-explain.html": "/docs/18/sql-explain.html", "/zh/docs/18/using-explain.html": "/docs/18/using-explain.html"}, "body_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/18/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "body_sha256": "a307beecc8c4bd0f009fe669db7f60dab07420db237eefe0dcb42036ec86d41d", "content_hash": "cbf05e93c65e58ee4a493331796098a26a165c5e4cd6bd4cfe03c6f57db95840", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Subquery Scan", "identity": "Subquery Scan"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "strategies": [], "description": ["\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002"], "sections_zh": [{"title": "EXPLAIN \u540d\u79f0\u4e0e\u5c5e\u6027", "paragraphs": ["\u7ed3\u6784\u5316\u683c\u5f0f\u4f7f\u7528\u4e0a\u8ff0 Node Type\u3002\u6587\u672c\u683c\u5f0f\u540d\u79f0\u8fd8\u53ef\u80fd\u5305\u542b\u64cd\u4f5c\u3001\u7b56\u7565\u3001\u8fde\u63a5\u7c7b\u578b\u3001\u626b\u63cf\u65b9\u5411\u6216\u805a\u5408\u9636\u6bb5\u5c5e\u6027\u3002", "\u6b64\u6e90\u7801\u8bb0\u5f55\u7684\u6587\u672c\u540d\u79f0\uff1aSubquery Scan.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeSubqueryscan.c\uff1a\u652f\u6301\u626b\u63cf\u5b50\u67e5\u8be2\uff08\u8303\u56f4\u8868\u4e2d\u7684\u5b50 SELECT\uff09\u7684\u4f8b\u7a0b\u3002", "\u8fd9\u4e0e\u5b50\u94fe\u63a5\uff08nodeSubplan.c\uff09\u7a0d\u6709\u5dee\u522b\uff0c\u56e0\u6b64\u9700\u8981\u4e24\u5957\u4ee3\u7801\u3002\u5e94\u8003\u8651\u5c1d\u8bd5\u5c06\u8fd9\u4e9b\u60c5\u51b5\u7edf\u4e00\u3002", "\u76f4\u63a5\u8fd4\u56de\u5b50\u8ba1\u5212\u7684\u7ed3\u679c\u69fd\u4f4d\uff0c\u907f\u514d ExecCopySlot() \u7684\u989d\u5916\u5f00\u9500\u3002\uff08\u8282\u70b9\u81ea\u8eab\u7684 ScanTupleSlot \u4ec5\u7528\u4e8e EvalPlanQual \u91cd\u65b0\u68c0\u67e5\u3002\uff09", "SubqueryRecheck\uff1a\u5728 EvalPlanQual \u4e2d\u91cd\u65b0\u68c0\u67e5\u5143\u7ec4\u7684\u8bbf\u95ee\u65b9\u6cd5\u4f8b\u7a0b\u3002", "\u987a\u5e8f\u626b\u63cf\u5b50\u67e5\u8be2\u5e76\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4\u3002\u8c03\u7528 ExecScan() \u5e76\u4f20\u5165\u76f8\u5e94\u7684\u8bbf\u95ee\u65b9\u6cd5\u51fd\u6570\u3002"]}, {"code": "case T_SubqueryScan:\n\t\t\tpname = sname = \"Subquery Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/18/description/0": "Scans the output of a subquery plan.", "/versions/18/facts/0/label": "Core node tag", "/versions/18/facts/1/label": "Structured EXPLAIN Node Type", "/versions/18/facts/2/label": "Inputs", "/versions/18/facts/2/value": "A subquery child plan", "/versions/18/facts/3/label": "Output", "/versions/18/facts/3/value": "Subquery result tuples", "/versions/18/facts/4/label": "Executor initializer", "/versions/18/facts/5/label": "Memory mechanism", "/versions/18/tables/0/title": "EXPLAIN labels in this source build", "/versions/18/related/1/label": "Using EXPLAIN", "/versions/18/related/2/label": "Parallel plans", "/versions/18/sections/0/title": "EXPLAIN names and attributes", "/versions/18/sections/1/title": "Memory and temporary storage", "/versions/18/sections/2/title": "Parallel execution and instrumentation", "/versions/18/sections/3/title": "Executor implementation notes", "/versions/18/sections/4/title": "EXPLAIN identity in core source", "/versions/18/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/18/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/18/sections/0/paragraphs/1": "Text names recorded by this source: Subquery Scan.", "/versions/18/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/18/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/18/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/18/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/18/sections/3/paragraphs/0": "nodeSubqueryscan.c Support routines for scanning subqueries (subselects in rangetable).", "/versions/18/sections/3/paragraphs/1": "This is just enough different from sublinks (nodeSubplan.c) to mean that we need two sets of code. Ought to look at trying to unify the cases.", "/versions/18/sections/3/paragraphs/2": "We just return the subplan's result slot, rather than expending extra cycles for ExecCopySlot(). (Our own ScanTupleSlot is used only for EvalPlanQual rechecks.)", "/versions/18/sections/3/paragraphs/3": "SubqueryRecheck -- access method routine to recheck a tuple in EvalPlanQual", "/versions/18/sections/3/paragraphs/4": "Scans the subquery sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "/versions/18/tables/0/columns/0/label": "Text-format label", "/versions/18/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "69301e70f0200d5845e679ff940a2d05cc2ab7e7c6ac58394fa39691e17c321e", "canonical_center_text_hash": "cbf05e93c65e58ee4a493331796098a26a165c5e4cd6bd4cfe03c6f57db95840"}, "evidence_kind": "source and documentation", "explain_names": ["Subquery Scan"], "partial_modes": [], "description_zh": "\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002", "comparison_data": {"node_tag": "T_SubqueryScan", "strategies": [], "text_names": ["Subquery Scan"], "initializer": "ExecInitSubqueryScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "2c67fdef6b55d5dfeedc05274c332f8e523a7b8dd3ffef1c7cb79b9d6d33566f", "manual_language": "zh", "explain_prefixes": ["Parallel", "Async"], "runtime_verified": false, "source_inventory": {"explain": "src/backend/commands/explain.c", "executor": "src/backend/executor/execProcnode.c", "implementation": "src/backend/executor/nodeSubqueryscan.c"}, "parallel_callbacks": [], "description_zh_html": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/zh/docs/18/sql-explain.html\" rel=\"nofollow\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html\" rel=\"nofollow\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>", "center_zh_rendered": "<p>\u626b\u63cf\u5b50\u67e5\u8be2\u8ba1\u5212\u7684\u8f93\u51fa\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_SubqueryScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Subquery Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a\u8be5\u8282\u70b9\u5b9e\u73b0\u4e2d\u672a\u63d0\u53d6\u5230\u6b64\u7c7b\u56de\u8c03\u3002\u56de\u8c03\u7684\u5b58\u5728\u4e0d\u8868\u793a\u8be5\u8282\u70b9\u5fc5\u7136\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\uff1b\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u4e2d\u6267\u884c\u4e5f\u4e0d\u7b49\u4e8e\u5177\u6709\u5e76\u884c\u611f\u77e5\u80fd\u529b\u3002</p><h3>\u540c\u7248\u672c\u4e2d\u6587\u624b\u518c\u8282\u9009</h3><p>\n<span>PostgreSQL</span> \u4f1a\u4e3a\u6536\u5230\u7684\u6bcf\u4e2a\u67e5\u8be2\u5236\u5b9a\u4e00\u4e2a<em>\u67e5\u8be2\u8ba1\u5212</em>\u3002\u9009\u62e9\u4e0e\u67e5\u8be2\u7ed3\u6784\u548c\u6570\u636e\u7279\u6027\u76f8\u5339\u914d\u7684\u6b63\u786e\u8ba1\u5212\uff0c\u5bf9\u83b7\u5f97\u826f\u597d\u7684\u6027\u80fd\u81f3\u5173\u91cd\u8981\uff0c\u56e0\u6b64\u7cfb\u7edf\u5185\u7f6e\u4e86\u4e00\u4e2a\u590d\u6742\u7684<em>\u89c4\u5212\u5668</em>\u6765\u5c3d\u91cf\u9009\u51fa\u597d\u7684\u8ba1\u5212\u3002\u53ef\u4ee5\u4f7f\u7528 <a href=\"/docs/18/sql-explain.html\"><code>EXPLAIN</code></a> \u547d\u4ee4\u67e5\u770b\u89c4\u5212\u5668\u4e3a\u4efb\u610f\u67e5\u8be2\u751f\u6210\u7684\u67e5\u8be2\u8ba1\u5212\u3002\u8bfb\u61c2\u8ba1\u5212\u662f\u4e00\u95e8\u9700\u8981\u7ecf\u9a8c\u79ef\u7d2f\u7684\u6280\u80fd\uff0c\u672c\u8282\u5c06\u5c1d\u8bd5\u4ecb\u7ecd\u5176\u4e2d\u7684\u57fa\u7840\u77e5\u8bc6\u3002\n   </p><p>\n    \u672c\u8282\u4e2d\u7684\u793a\u4f8b\u53d6\u81ea\u6267\u884c\u8fc7 <code>VACUUM ANALYZE</code> \u7684\u56de\u5f52\u6d4b\u8bd5\u6570\u636e\u5e93\uff0c\u4f7f\u7528\u7684\u662f v18 \u5f00\u53d1\u7248\u672c\u6e90\u7801\u3002\u5982\u679c\u81ea\u884c\u5c1d\u8bd5\u8fd9\u4e9b\u793a\u4f8b\uff0c\u901a\u5e38\u5e94\u5f53\u80fd\u5f97\u5230\u76f8\u8fd1\u7684\u7ed3\u679c\uff0c\u4f46\u4f30\u8ba1\u4ee3\u4ef7\u548c\u884c\u8ba1\u6570\u53ef\u80fd\u7565\u6709\u5dee\u5f02\uff0c\u56e0\u4e3a <code>ANALYZE</code> \u751f\u6210\u7684\u7edf\u8ba1\u4fe1\u606f\u6765\u81ea\u968f\u673a\u91c7\u6837\u800c\u975e\u7cbe\u786e\u8ba1\u6570\uff0c\u800c\u4e14\u4ee3\u4ef7\u672c\u8eab\u5728\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4e5f\u4f9d\u8d56\u4e8e\u5e73\u53f0\u3002\n   </p><p>\n    \u8fd9\u4e9b\u793a\u4f8b\u4f7f\u7528 <code>EXPLAIN</code> \u9ed8\u8ba4\u7684<span>\u201c<span>text</span>\u201d</span>\u8f93\u51fa\u683c\u5f0f\uff0c\u5b83\u7d27\u51d1\u4e14\u4fbf\u4e8e\u4eba\u5de5\u9605\u8bfb\u3002\u5982\u679c\u5e0c\u671b\u5c06 <code>EXPLAIN</code> \u7684\u8f93\u51fa\u4ea4\u7ed9\u7a0b\u5e8f\u505a\u8fdb\u4e00\u6b65\u5206\u6790\uff0c\u5219\u5e94\u6539\u7528\u673a\u5668\u53ef\u8bfb\u7684\u8f93\u51fa\u683c\u5f0f\uff08XML\u3001JSON \u6216 YAML\uff09\u3002\n   </p><p><a href=\"/docs/18/using-explain.html\">\u67e5\u770b\u5b8c\u6574\u4e2d\u6587\u624b\u518c\u4e0e\u4e0a\u4e0b\u6587</a>\u3002</p><p>\u672c\u9875\u5f00\u5934\u7684\u4e2d\u6587\u8bf4\u660e\u4e3a PG.CENTER \u5bf9\u7f16\u8f91\u8bf4\u660e\u7684\u7ffb\u8bd1\uff1b\u624b\u518c\u8282\u9009\u4fdd\u7559\u5bf9\u5e94\u7248\u672c\u4e2d\u6587\u6587\u6863\u539f\u6587\u3002\u6e90\u7801\u4fe1\u606f\u53ca\u624b\u518c\u793a\u4f8b\u4e0d\u4ee3\u8868\u91cd\u65b0\u8fdb\u884c\u8fc7\u8fd0\u884c\u6d4b\u8bd5\u3002</p>"}, "comparison": {"left": "17", "right": "18", "status": "unchanged", "diff": ""}}