{"kind": "plan", "major": "18", "item": {"slug": "index-only-scan", "name": "Index Only Scan", "name_zh": "IndexOnlyScan", "category": "\u626b\u63cf", "summary": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "aliases": ["Index Only Scan", "IndexOnlyScan", "T_IndexOnlyScan"], "content_hash": "de59b9d1a28a4ab4d5b940231133c33c45616d478c85a9318e151102f0c00bf3", "versions": {"10": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"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/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "55150187649bd22c0579d10310a11718f5fe50c99ea7c70ac6aa7a34ff1723ec", "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=10", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=10", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=10", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "line": 947, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:947", "sha256": "a785298532047cfeda969e78c3597a343dc1c56d61ba85830b0f16a02a14b5a1", "archive_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, {"url": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "line": 222, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:222", "sha256": "cea76648bb38ae55f18f989768bee1a4ee025691ceea0f86bccb29dcdc166acc", "archive_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, {"url": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "55150187649bd22c0579d10310a11718f5fe50c99ea7c70ac6aa7a34ff1723ec", "archive_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, {"url": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "d562c321108844798cd234303fffb618f13d4ee3f3a5ac79bfd963b077e47c22", "archive_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}], "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": "9a80bc0971efb26e0f20982525e3b10913dd2e4b77f518b6f6e11dbf5cdd0f95", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "10", "text_hash": "0a7d4d1e582635658e091dc3ad210ec3b3c0e5adf2ce8150dab60e0076b984d1", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": "9a80bc0971efb26e0f20982525e3b10913dd2e4b77f518b6f6e11dbf5cdd0f95", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "5989b3a19303548b2fe8a86baf2eea697c3c800e340128ff87d5580740bb277b", "content_hash": "0a7d4d1e582635658e091dc3ad210ec3b3c0e5adf2ce8150dab60e0076b984d1", "source_database": "center", "source_revision": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only 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": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/10/facts/3/label": "Output", "/versions/10/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM.", "/versions/10/sections/3/paragraphs/0": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/10/sections/3/paragraphs/1": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/10/sections/3/paragraphs/2": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/10/sections/3/paragraphs/3": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/10/sections/3/paragraphs/4": "We need to detect clearing a VM bit due to an insert right away, because the tuple is present in the index page but not visible. The reading of the TID by this scan (using a shared lock on the index buffer) is serialized with the insert of the TID into the index (using an exclusive lock on the index buffer). Because the VM bit is cleared before updating the index, and locking/unlocking of the index page acts as a full memory barrier, we are sure to see the cleared bit if we see a recently-inserted TID.", "/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": "9d1bfd5fc07edab42f7d44a365cbf195a14eb8486a9986a81a43390abbfef128", "canonical_center_text_hash": "0a7d4d1e582635658e091dc3ad210ec3b3c0e5adf2ce8150dab60e0076b984d1"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"]}, "comparison_hash": "aa21a339252c1b45b1415cfaeeb65e278cc05df0ac3477c15dc983b5b8fb5609", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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>"}, "11": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "7ef7067eff7d83c4a5e1c4016db924d16a9637318e6dcc7bd1287c1c24b226a1", "archive_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}], "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": "Index Only Scan", "identity": "Index Only 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=11", "label": "EXPLAIN"}, {"url": "/docs/11/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/11/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=11", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=11", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=11", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "release": {"ref": "PostgreSQL 11.22 source archive", "label": "11.22", "major": "11", "channel": "historical", "revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0", "source_url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "line": 1072, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1072", "sha256": "9df8400c1a4377179572ceb916d6020fca4e2760f74bf416d77ed97476523bbd", "archive_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, {"url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "line": 222, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:222", "sha256": "95ef4d4a5df4c29f14af9763fae2c530449bdacdf3853d9ff297adf1fed6153b", "archive_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, {"url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "7ef7067eff7d83c4a5e1c4016db924d16a9637318e6dcc7bd1287c1c24b226a1", "archive_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, {"url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "5e0511194183800e8d6eb293fd4b40639c7d3118e2d199c8e7865ba4fa4cf67f", "archive_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}], "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": "6b229fa4f10474afa848b7e0345cd07fc5672fabeec6a6e8f3dfb0d13db629f1", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "11", "text_hash": "9f5eb9597680a86e02af6f031a4802f9e575440af74be9e0253a6cad32f9159e", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": "6b229fa4f10474afa848b7e0345cd07fc5672fabeec6a6e8f3dfb0d13db629f1", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "19880597acd6f001115408b201d1776101246f5548923c054d865c98743ae030", "content_hash": "9f5eb9597680a86e02af6f031a4802f9e575440af74be9e0253a6cad32f9159e", "source_database": "center", "source_revision": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only 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": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/11/facts/3/label": "Output", "/versions/11/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM.", "/versions/11/sections/3/paragraphs/0": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/11/sections/3/paragraphs/1": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/11/sections/3/paragraphs/2": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/11/sections/3/paragraphs/3": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/11/sections/3/paragraphs/4": "We need to detect clearing a VM bit due to an insert right away, because the tuple is present in the index page but not visible. The reading of the TID by this scan (using a shared lock on the index buffer) is serialized with the insert of the TID into the index (using an exclusive lock on the index buffer). Because the VM bit is cleared before updating the index, and locking/unlocking of the index page acts as a full memory barrier, we are sure to see the cleared bit if we see a recently-inserted TID.", "/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": "92de98415204e6864f1f6eb338bd8d3cd3235167c4167af4a873014f25de52a1", "canonical_center_text_hash": "9f5eb9597680a86e02af6f031a4802f9e575440af74be9e0253a6cad32f9159e"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"]}, "comparison_hash": "aa21a339252c1b45b1415cfaeeb65e278cc05df0ac3477c15dc983b5b8fb5609", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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>"}, "12": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "5f8788ae417b7dcff7dee6e83a524dbf3e574f5d3dacb111ec6e70621e8ff795", "archive_sha256": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}], "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=12", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=12", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=12", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "line": 1143, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1143", "sha256": "d02ea84fdaa201de5d9360645a9f24bfbd2c31f7d45a639e09560ac0e6b6471d", "archive_sha256": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, {"url": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "line": 222, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:222", "sha256": "311b17379fe54e3f342fe5ad41c43afbdfa1b844978db2bb2eb22b82520d3256", "archive_sha256": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, {"url": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "5f8788ae417b7dcff7dee6e83a524dbf3e574f5d3dacb111ec6e70621e8ff795", "archive_sha256": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, {"url": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "b0c4a0aeb48660ce06e5e700d5529ca9066fd16682bd15783d6e71b5420b07b0", "archive_sha256": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}], "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": "75d3e03a61c840381a2aec90cdb650bbd7826583359340d543b0821bc5c77c7b", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "12", "text_hash": "f843d95dac4cc414f5eefa11417769edf3ccefc373643fa26e100ffdcd4a880b", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": "75d3e03a61c840381a2aec90cdb650bbd7826583359340d543b0821bc5c77c7b", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "cabfc2348601a2d95e076527f37a09def64b94765114237252cd358620bdc146", "content_hash": "f843d95dac4cc414f5eefa11417769edf3ccefc373643fa26e100ffdcd4a880b", "source_database": "center", "source_revision": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only 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": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/12/facts/3/label": "Output", "/versions/12/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM.", "/versions/12/sections/3/paragraphs/0": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/12/sections/3/paragraphs/1": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/12/sections/3/paragraphs/2": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/12/sections/3/paragraphs/3": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/12/sections/3/paragraphs/4": "We need to detect clearing a VM bit due to an insert right away, because the tuple is present in the index page but not visible. The reading of the TID by this scan (using a shared lock on the index buffer) is serialized with the insert of the TID into the index (using an exclusive lock on the index buffer). Because the VM bit is cleared before updating the index, and locking/unlocking of the index page acts as a full memory barrier, we are sure to see the cleared bit if we see a recently-inserted TID.", "/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": "35d7553e4ba1bca7f208409411cfc2fe5130a2d1764e8d1759de29e33f280976", "canonical_center_text_hash": "f843d95dac4cc414f5eefa11417769edf3ccefc373643fa26e100ffdcd4a880b"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"]}, "comparison_hash": "aa21a339252c1b45b1415cfaeeb65e278cc05df0ac3477c15dc983b5b8fb5609", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"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/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "75be9ae9eb331f913f5518f81b45a73afd53c919425633121582bb02aeb6beea", "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=13", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=13", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=13", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": "https://ftp.postgresql.org/pub/source/v13.23/postgresql-13.23.tar.bz2", "line": 1201, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1201", "sha256": "541713e0e7f1c9cc352c2b6028964d440c19d2678a4463000094c24a88c1e730", "archive_sha256": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, {"url": "https://ftp.postgresql.org/pub/source/v13.23/postgresql-13.23.tar.bz2", "line": 222, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:222", "sha256": "d085ee99acfa00587e6ade3a1d9f8108a0566beedbbee3f54a50c9fc0cc2e875", "archive_sha256": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, {"url": "https://ftp.postgresql.org/pub/source/v13.23/postgresql-13.23.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "75be9ae9eb331f913f5518f81b45a73afd53c919425633121582bb02aeb6beea", "archive_sha256": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, {"url": "https://ftp.postgresql.org/pub/source/v13.23/postgresql-13.23.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "dcb296833777b02008c4b6bae8e8f7c6423b7ffba21f36702597c9d596d039ab", "archive_sha256": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/13/performance-tips.html#USING-EXPLAIN", "anchor": "USING-EXPLAIN", "locale": "zh-Hans", "version": "13", "build_id": 66, "page_key": "performance-tips.html", "extraction": "concept-introduction", "source_hash": "d7400476f3cf658423dd2d2f64b6b6b0e53d8fdc8692b9e93a05587095d469e1", "fragment_sha256": "9385d1b095126378694216a1f9cb95d249ccc7fab5ffa3f65cf08679fe2b14c3", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "snapshot:sha256:a13a825c39f0268ef1cfe9137e283e38d0da73b2d7894f0733c7b26372a4f6a4", "translated_from_revision": null}, "body_sha256": "d705fc9d7123d66a85a9755e431d73043dd374d0322a9ebb82d558169995df72", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "13", "text_hash": "6c7567b65abd23c7f71dd5d1ca46dcd65c244420f327f1aaa318f551702e59dc", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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/13/performance-tips.html#USING-EXPLAIN", "anchor": "USING-EXPLAIN", "locale": "zh-Hans", "version": "13", "build_id": 66, "page_key": "performance-tips.html", "extraction": "concept-introduction", "source_hash": "d7400476f3cf658423dd2d2f64b6b6b0e53d8fdc8692b9e93a05587095d469e1", "fragment_sha256": "9385d1b095126378694216a1f9cb95d249ccc7fab5ffa3f65cf08679fe2b14c3", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "snapshot:sha256:a13a825c39f0268ef1cfe9137e283e38d0da73b2d7894f0733c7b26372a4f6a4", "translated_from_revision": null}, "body_sha256": "d705fc9d7123d66a85a9755e431d73043dd374d0322a9ebb82d558169995df72", "runtime_rerun": false, "authored_translation": "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "383435c7533454dce941f8aa64e962d6f0863fd3b344832901f5f0b2eba50f63", "content_hash": "6c7567b65abd23c7f71dd5d1ca46dcd65c244420f327f1aaa318f551702e59dc", "source_database": "center", "source_revision": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only 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": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/13/facts/3/label": "Output", "/versions/13/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM.", "/versions/13/sections/3/paragraphs/0": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/13/sections/3/paragraphs/1": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/13/sections/3/paragraphs/2": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/13/sections/3/paragraphs/3": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/13/sections/3/paragraphs/4": "We need to detect clearing a VM bit due to an insert right away, because the tuple is present in the index page but not visible. The reading of the TID by this scan (using a shared lock on the index buffer) is serialized with the insert of the TID into the index (using an exclusive lock on the index buffer). Because the VM bit is cleared before updating the index, and locking/unlocking of the index page acts as a full memory barrier, we are sure to see the cleared bit if we see a recently-inserted TID.", "/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": "dee26e91dc9e2a782b7ecd81ff56fef6af5b2e0450688d0036c983c333855210", "canonical_center_text_hash": "6c7567b65abd23c7f71dd5d1ca46dcd65c244420f327f1aaa318f551702e59dc"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"]}, "comparison_hash": "aa21a339252c1b45b1415cfaeeb65e278cc05df0ac3477c15dc983b5b8fb5609", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"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/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "38bb1b9d21aab273323e0ad1efe60cecb60055f8e50fbd74bb48577209c8b6a6", "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=14", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=14", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=14", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": 1237, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1237", "sha256": "e091be4e2a083b8dea39ccd09beedede22c1716ef974da66c214a44f48be8c41", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, {"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "line": 224, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:224", "sha256": "72da1c5ad457f1d92a39ab73531701794df858419e3b89d6e6cb7079634e68fa", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, {"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "38bb1b9d21aab273323e0ad1efe60cecb60055f8e50fbd74bb48577209c8b6a6", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, {"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "302f51a16b570dba7ec4e7bc045f7df5800d21630280354d1a24025f3baec75d", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}], "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": "f5fc16dfa1d591b024a64389276925ca68cbaf36acb4f510fb80b877bc96c88c", "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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "14", "text_hash": "ccc675bb7af24a9f537cfdc1f2ce99250b4b3f554f82204af56ad16ecbbba9af", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": "f5fc16dfa1d591b024a64389276925ca68cbaf36acb4f510fb80b877bc96c88c", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "a8f545e6cdaf8528ad34569c3d08cb72c95074881dfb1281cdf67ac47c1c81dd", "content_hash": "ccc675bb7af24a9f537cfdc1f2ce99250b4b3f554f82204af56ad16ecbbba9af", "source_database": "center", "source_revision": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only 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": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/14/facts/3/label": "Output", "/versions/14/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM.", "/versions/14/sections/3/paragraphs/0": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/14/sections/3/paragraphs/1": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/14/sections/3/paragraphs/2": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/14/sections/3/paragraphs/3": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/14/sections/3/paragraphs/4": "We need to detect clearing a VM bit due to an insert right away, because the tuple is present in the index page but not visible. The reading of the TID by this scan (using a shared lock on the index buffer) is serialized with the insert of the TID into the index (using an exclusive lock on the index buffer). Because the VM bit is cleared before updating the index, and locking/unlocking of the index page acts as a full memory barrier, we are sure to see the cleared bit if we see a recently-inserted TID.", "/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": "fad32b46f034c5fe17148111190181ee3c18ea79ff5ed5818af392d52da2b958", "canonical_center_text_hash": "ccc675bb7af24a9f537cfdc1f2ce99250b4b3f554f82204af56ad16ecbbba9af"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"]}, "comparison_hash": "aa21a339252c1b45b1415cfaeeb65e278cc05df0ac3477c15dc983b5b8fb5609", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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>"}, "15": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "7f42eaea2c6e8a2c13238ec2c146fb89d81f28471db60978a4b2c1657e375187", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}], "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": "Index Only Scan", "identity": "Index Only 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=15", "label": "EXPLAIN"}, {"url": "/docs/15/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/15/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=15", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=15", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=15", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "release": {"ref": "PostgreSQL 15.19 source archive", "label": "15.19", "major": "15", "channel": "stable", "revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89", "source_url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "line": 1240, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1240", "sha256": "bb3b442d0f1b098aa8707335250102f027a596cd94117308bd16d1d36b258f5c", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, {"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "line": 224, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:224", "sha256": "19836c50a272741a4eac653541e655437c2e00710a541e5348d6a277d0669d7c", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, {"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "7f42eaea2c6e8a2c13238ec2c146fb89d81f28471db60978a4b2c1657e375187", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, {"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "fb4a4c8165495299131173680bc02a950d88e1ff610231fd97997bc0c9afc1d7", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}], "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": "a2f63a9b6d331b8ddd00547e2e96e4e19918f0cacdf01a474a68781541e39eb8", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "15", "text_hash": "6b92c4e0c0ac9ad1df4ca9891ac7ddeb93b2644a078febbaa9a8f41bedf6a69a", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": "a2f63a9b6d331b8ddd00547e2e96e4e19918f0cacdf01a474a68781541e39eb8", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "7a69e6c1fe266657f639383f2f32059b4f6c62c73217442011c67bdc171acd52", "content_hash": "6b92c4e0c0ac9ad1df4ca9891ac7ddeb93b2644a078febbaa9a8f41bedf6a69a", "source_database": "center", "source_revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002", "\u5fc5\u987b\u7acb\u5373\u68c0\u6d4b\u63d2\u5165\u64cd\u4f5c\u6e05\u9664 VM \u4f4d\u7684\u60c5\u51b5\uff0c\u56e0\u4e3a\u5143\u7ec4\u867d\u5df2\u51fa\u73b0\u5728\u7d22\u5f15\u9875\u4e2d\uff0c\u5374\u5c1a\u4e0d\u53ef\u89c1\u3002\u672c\u6b21\u626b\u63cf\u8bfb\u53d6 TID \u65f6\u5bf9\u7d22\u5f15\u7f13\u51b2\u533a\u52a0\u5171\u4eab\u9501\uff0c\u5411\u7d22\u5f15\u63d2\u5165 TID \u65f6\u52a0\u6392\u4ed6\u9501\uff0c\u4e24\u8005\u4e32\u884c\u5316\u3002VM \u4f4d\u5728\u66f4\u65b0\u7d22\u5f15\u4e4b\u524d\u5df2\u6e05\u9664\uff0c\u800c\u7d22\u5f15\u9875\u7684\u52a0\u9501\u548c\u89e3\u9501\u6784\u6210\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff0c\u56e0\u6b64\u770b\u5230\u65b0\u63d2\u5165\u7684 TID \u65f6\uff0c\u5fc5\u7136\u4e5f\u4f1a\u770b\u5230\u5df2\u6e05\u9664\u7684 VM \u4f4d\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only 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": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/15/facts/3/label": "Output", "/versions/15/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM.", "/versions/15/sections/3/paragraphs/0": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/15/sections/3/paragraphs/1": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/15/sections/3/paragraphs/2": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/15/sections/3/paragraphs/3": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/15/sections/3/paragraphs/4": "We need to detect clearing a VM bit due to an insert right away, because the tuple is present in the index page but not visible. The reading of the TID by this scan (using a shared lock on the index buffer) is serialized with the insert of the TID into the index (using an exclusive lock on the index buffer). Because the VM bit is cleared before updating the index, and locking/unlocking of the index page acts as a full memory barrier, we are sure to see the cleared bit if we see a recently-inserted TID.", "/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": "a5d35b12e67affea46f6ddeac481e14f97cc077867504aceb1b8d6bbc9e2d262", "canonical_center_text_hash": "6b92c4e0c0ac9ad1df4ca9891ac7ddeb93b2644a078febbaa9a8f41bedf6a69a"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"]}, "comparison_hash": "aa21a339252c1b45b1415cfaeeb65e278cc05df0ac3477c15dc983b5b8fb5609", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"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/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "31c763bfa8c3fc7ad81254e27f82f8f093c3667c9274fa288c918d1506e28130", "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=16", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=16", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=16", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": 1273, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1273", "sha256": "8e017f0116dbea471339b40c37a667cc9f95039e7e0329c783e5e8ce194de7e1", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, {"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "line": 224, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:224", "sha256": "e48c08e555f8cb4e4bb43df516c4b8906ce9bc374b2a745d98a1fc8c22cc5099", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, {"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "31c763bfa8c3fc7ad81254e27f82f8f093c3667c9274fa288c918d1506e28130", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, {"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "97db47353db76326b874589a5ad0a04501cc74cd72e237e7bd956e7472c41f1f", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/16/using-explain.html", "anchor": "", "locale": "zh-Hans", "version": "16", "build_id": 103, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "394de9d6895c7909a1a823408b8c980c5415db8ca3c212e23d6e7e9b6e01c6cc", "fragment_sha256": "8a4cc7ad0a2c8ca5894434db8a1fca93a69bfb200ac510843c26d7bd42a12d58", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:80579a071736780f9c4022bb5148e1fb1256f1a33591306af67816e9e9bf3a9b", "translated_from_revision": null}, "body_sha256": "41ffcc3e472d4360a479ca5b0397942ed282f7a4ada5925bd65ceac53a20709c", "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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "16", "text_hash": "93dafb2a0e4967be90ba80fc96ab2eb73798839b6bda1d323da9b3a2a23478d3", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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/16/using-explain.html", "anchor": "", "locale": "zh-Hans", "version": "16", "build_id": 103, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "394de9d6895c7909a1a823408b8c980c5415db8ca3c212e23d6e7e9b6e01c6cc", "fragment_sha256": "8a4cc7ad0a2c8ca5894434db8a1fca93a69bfb200ac510843c26d7bd42a12d58", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:80579a071736780f9c4022bb5148e1fb1256f1a33591306af67816e9e9bf3a9b", "translated_from_revision": null}, "body_sha256": "41ffcc3e472d4360a479ca5b0397942ed282f7a4ada5925bd65ceac53a20709c", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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": "a77133aeeae30f4238b4c821499909901f6b3867fad944bd8d01f7e2564508a0", "content_hash": "93dafb2a0e4967be90ba80fc96ab2eb73798839b6bda1d323da9b3a2a23478d3", "source_database": "center", "source_revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only 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": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/16/facts/3/label": "Output", "/versions/16/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM.", "/versions/16/sections/3/paragraphs/0": "Determine which direction to scan the index in based on the plan's scan direction and the current direction of execution.", "/versions/16/sections/3/paragraphs/1": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/16/sections/3/paragraphs/2": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/16/sections/3/paragraphs/3": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/16/sections/3/paragraphs/4": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/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": "154ca6ba9a875ae028c8b52591584f55b2d8d31f8cdcda8d5e6632fede59c836", "canonical_center_text_hash": "93dafb2a0e4967be90ba80fc96ab2eb73798839b6bda1d323da9b3a2a23478d3"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"]}, "comparison_hash": "aa21a339252c1b45b1415cfaeeb65e278cc05df0ac3477c15dc983b5b8fb5609", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"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/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "14da0be98437e1a8db705baf16767198099eeaa24449e0d3c7dc04b846dda1a3", "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=17", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=17", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=17", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": 1462, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1462", "sha256": "741251b1a3b6d269a52a673d42eb63b02e13a5872db7b359b137086ab21b63c8", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, {"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "line": 224, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:224", "sha256": "a77576e158b94cb01fa8c5174ba133004eabdd727660323f8afc66c8d2e757b8", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, {"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "14da0be98437e1a8db705baf16767198099eeaa24449e0d3c7dc04b846dda1a3", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, {"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "d390dd69e2d3f5085beb42b33e46ff0676a2959b916a12b82118a7e545f8e562", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, {"url": "/docs/17/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 17.11 \u00b7 using-explain", "sha256": "8e3422c77496cc53bfc225ccadda3e82eb23c8c362b8eb95e7fb02cdb315ea78"}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/17/using-explain.html#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "17", "build_id": 105, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "b1252952c6d796f5e38c223b74ff667f2d19d677dcf85fe5269b782b830e5013", "fragment_sha256": "e2870d066840aa2e3c31457a93d824938a26590ee10ed3e1dffd5782ea3e1ee2", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:7340767258d21c21b36f373f1fff6bab2be18e0daca13a865129db6105c09efd", "translated_from_revision": null}, "body_sha256": "e05c1c5259afa6624433e6c24658ed11352bc7f106638f19c0fc3f5878e5cd11", "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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/17/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 17.11 \u00b7 using-explain", "sha256": "8e3422c77496cc53bfc225ccadda3e82eb23c8c362b8eb95e7fb02cdb315ea78"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 17.11 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "17", "text_hash": "2937a887e54ffd3d3e9e79ad76977d9c346d9a67b99977c1b119a9c05d46266f", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "17", "build_id": 105, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "b1252952c6d796f5e38c223b74ff667f2d19d677dcf85fe5269b782b830e5013", "fragment_sha256": "e2870d066840aa2e3c31457a93d824938a26590ee10ed3e1dffd5782ea3e1ee2", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:7340767258d21c21b36f373f1fff6bab2be18e0daca13a865129db6105c09efd", "translated_from_revision": null}, "body_sha256": "e05c1c5259afa6624433e6c24658ed11352bc7f106638f19c0fc3f5878e5cd11", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/17/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 17.11 \u00b7 using-explain", "sha256": "8e3422c77496cc53bfc225ccadda3e82eb23c8c362b8eb95e7fb02cdb315ea78"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 17.11 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em class=\"firstterm\">\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code class=\"literal\">VALUES</code> \u5b50\u53e5\u548c <code class=\"literal\">FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code class=\"command\">EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code class=\"literal\">WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a class=\"xref\" href=\"/zh/docs/17/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a class=\"xref\" href=\"/zh/docs/17/runtime-config-query.html#GUC-SEQ-PAGE-COST\">seq_page_cost</a> \u8bbe\u4e3a <code class=\"literal\">1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/17/using-explain.html#USING-EXPLAIN-BASICS\">\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "version": "17", "link_map": {"/zh/docs/17/using-explain.html#USING-EXPLAIN-BASICS": "/docs/17/using-explain.html#USING-EXPLAIN-BASICS", "/zh/docs/17/runtime-config-query.html#GUC-SEQ-PAGE-COST": "/docs/17/runtime-config-query.html#GUC-SEQ-PAGE-COST", "/zh/docs/17/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS": "/docs/17/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS"}, "body_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/17/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/17/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/17/using-explain.html#USING-EXPLAIN-BASICS\" 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": "008cbe041a157e4c748c453a07ffa4adb2f794055b8e7f660b6e1c49fd880deb", "content_hash": "2937a887e54ffd3d3e9e79ad76977d9c346d9a67b99977c1b119a9c05d46266f", "source_database": "center", "source_revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/17/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 17.11 \u00b7 using-explain", "sha256": "8e3422c77496cc53bfc225ccadda3e82eb23c8c362b8eb95e7fb02cdb315ea78"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 17.11 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [{"url": "/docs/17/using-explain.html", "method": "same-major semantic node", "sha256": "610ae355c419b53a5e213a8c8e2eacbf34e4fa0ac8f6d27365071bc6d3c90278", "language": "zh", "matched_nodes": ["#USING-EXPLAIN/div[7]/p[58]"]}], "language": "zh", "original_text": {"/versions/17/description/0": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/17/facts/3/label": "Output", "/versions/17/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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": "Examples from this manual build", "/versions/17/sections/4/title": "Executor implementation notes", "/versions/17/sections/5/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM.", "/versions/17/sections/4/paragraphs/0": "Determine which direction to scan the index in based on the plan's scan direction and the current direction of execution.", "/versions/17/sections/4/paragraphs/1": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/17/sections/4/paragraphs/2": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/17/sections/4/paragraphs/3": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/17/sections/4/paragraphs/4": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/17/tables/0/columns/0/label": "Text-format label", "/versions/17/tables/0/columns/1/label": "Structured node identity", "/versions/17/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 17.11 manual; it was not executed for this collection.", "/versions/17/sections/3/blocks/0/paragraphs/1": "In the example above, the ALL operator runs the subplan again for each row of the outer query (which accounts for the high estimated cost). Some queries can use a hashed subplan to avoid that:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "fff611ff0342ba536a2a14ca87c9ad858d481af7535af0e2bf3fa818c4f30857", "canonical_center_text_hash": "2937a887e54ffd3d3e9e79ad76977d9c346d9a67b99977c1b119a9c05d46266f"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"]}, "comparison_hash": "aa21a339252c1b45b1415cfaeeb65e278cc05df0ac3477c15dc983b5b8fb5609", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/17/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/17/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/17/using-explain.html#USING-EXPLAIN-BASICS\" 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>"}, "18": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "357d4ddbd6ba5d9b02f04185e579e2f2dc889d0d94875580770c8649cc427e6d", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}], "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=18", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=18", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=18", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "line": 1447, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1447", "sha256": "34c86d6070224a0e981efef51f79101d6d505e5874f1684ace183034bab14bb4", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "line": 224, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:224", "sha256": "f8a06a3f539077249b20664b2812433db6d7bd12b2c0ca633525db43d06f112a", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "357d4ddbd6ba5d9b02f04185e579e2f2dc889d0d94875580770c8649cc427e6d", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "52422b327a8049fbbb20d8b96008a0fc0a6fafa60f7eff3c695d5b2e83830120", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, {"url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "18", "build_id": 107, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "d2f749744b3ac5aa2eb0154f295e8163903cd20fcc130c74c6172cdf2ae3a9df", "fragment_sha256": "bc79b6f9c70f2b56968e08ea26d2c9ec3d395e425aca0594e227203daa0ad29b", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b", "translated_from_revision": null}, "body_sha256": "92dd757c4d84eb6e5a87e99db3bdc8fc9cb7eca771a3337aeb2b28c22032b6e7", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "18", "text_hash": "981a46151f5f56f4097f6d59815dc1618177e9984f6f208be3e5bfa55f861349", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "18", "build_id": 107, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "d2f749744b3ac5aa2eb0154f295e8163903cd20fcc130c74c6172cdf2ae3a9df", "fragment_sha256": "bc79b6f9c70f2b56968e08ea26d2c9ec3d395e425aca0594e227203daa0ad29b", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b", "translated_from_revision": null}, "body_sha256": "92dd757c4d84eb6e5a87e99db3bdc8fc9cb7eca771a3337aeb2b28c22032b6e7", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em class=\"firstterm\">\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code class=\"literal\">VALUES</code> \u5b50\u53e5\u548c <code class=\"literal\">FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code class=\"command\">EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code class=\"literal\">WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a class=\"xref\" href=\"/zh/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a class=\"xref\" href=\"/zh/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST\">seq_page_cost</a> \u8bbe\u4e3a <code class=\"literal\">1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS\">\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "version": "18", "link_map": {"/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "/zh/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST": "/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST", "/zh/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS": "/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS"}, "body_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS\" 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": "6562a9408ebc53c582c49aa54c6caea0900f02cb51edee4901e1e9e374a14c70", "content_hash": "981a46151f5f56f4097f6d59815dc1618177e9984f6f208be3e5bfa55f861349", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [{"url": "/docs/18/using-explain.html", "method": "same-major semantic node", "sha256": "b8835ec9adbc70ec150667a6b5443f8d298222dc0cc8c2bd1abb1c1d64895904", "language": "zh", "matched_nodes": ["#USING-EXPLAIN/div[7]/p[61]", "#USING-EXPLAIN/div[8]/p[13]"]}], "language": "zh", "original_text": {"/versions/18/description/0": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/18/facts/3/label": "Output", "/versions/18/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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": "Examples from this manual build", "/versions/18/sections/4/title": "Executor implementation notes", "/versions/18/sections/5/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation.", "/versions/18/sections/4/paragraphs/0": "Determine which direction to scan the index in based on the plan's scan direction and the current direction of execution.", "/versions/18/sections/4/paragraphs/1": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/18/sections/4/paragraphs/2": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/18/sections/4/paragraphs/3": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/18/sections/4/paragraphs/4": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/18/tables/0/columns/0/label": "Text-format label", "/versions/18/tables/0/columns/1/label": "Structured node identity", "/versions/18/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 18.6 manual; it was not executed for this collection.", "/versions/18/sections/3/blocks/0/paragraphs/1": "In the example above, the ALL operator runs the subplan again for each row of the outer query (which accounts for the high estimated cost). Some queries can use a hashed subplan to avoid that:", "/versions/18/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 18.6 manual; it was not executed for this collection.", "/versions/18/sections/3/blocks/1/paragraphs/1": "The \u201c Index Searches \u201d line is also useful with B-tree index scans that apply the skip scan optimization to more efficiently traverse through an index:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "0df59264ee459ceab9eafca048e06d3457cabcc265927bfcb60321745ce7cf40", "canonical_center_text_hash": "981a46151f5f56f4097f6d59815dc1618177e9984f6f208be3e5bfa55f861349"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM", "ExecIndexOnlyScanRetrieveInstrumentation"]}, "comparison_hash": "149a13d2842f396b0e35eb23a93337d9e8c708fbcf6665eec0ab0ebbd5320b9b", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM", "ExecIndexOnlyScanRetrieveInstrumentation"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS\" 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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/docs/18/using-explain.html#USING-EXPLAIN-BASICS\">\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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"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/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "882faa33a186834d3dd5f72fdc337441da4d39515ad02b672d5ca3c140b111cb", "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=19", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=19", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=19", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": 1459, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1459", "sha256": "8b115b1c194a4b54ae630209a741e293b1df49a9052f10b2de9ca092a48998e3", "archive_sha256": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, {"url": "https://ftp.postgresql.org/pub/source/v19rc1/postgresql-19rc1.tar.bz2", "line": 224, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:224", "sha256": "5e39b2037bed672da55104229ecc32da5abde44c26bcad01479edcfa044d09ed", "archive_sha256": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, {"url": "https://ftp.postgresql.org/pub/source/v19rc1/postgresql-19rc1.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "882faa33a186834d3dd5f72fdc337441da4d39515ad02b672d5ca3c140b111cb", "archive_sha256": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, {"url": "https://ftp.postgresql.org/pub/source/v19rc1/postgresql-19rc1.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "8d7bcf0e3b0d990a7bf35af47099d6d77207594b3136ff17104ed80bfaa47022", "archive_sha256": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, {"url": "/docs/19/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 19rc1 \u00b7 using-explain", "sha256": "aa29ae0e71c96497d59d957e6226a31c86894acefcffd1e819b009079cac3f27"}, {"url": "/docs/19/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 19rc1 \u00b7 using-explain", "sha256": "aa29ae0e71c96497d59d957e6226a31c86894acefcffd1e819b009079cac3f27"}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/19/using-explain.html#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "19", "build_id": 109, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "9bbb1ef5924e4788a3dc2642828383c67ab8651fb6b0e45924c454f095b0ff47", "fragment_sha256": "3fa71c2a92e6bb54ba04b9c118ed500d056ab0fefdeb59c70eea44ee96bcb510", "source_revision": "sha256:af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:65fda1f1b62a89992b84014c9157e61b67dbe8190e93945826efec668fad038c", "translated_from_revision": "sha256:af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "body_sha256": "a2a62af01091771b8cc6e23256eae119dbb1525a212d8e3e76cd9ea9a66136fa", "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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/19/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 19beta4 \u00b7 using-explain", "sha256": "52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 19beta4 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/19/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 19beta4 \u00b7 using-explain", "sha256": "52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 19beta4 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "19", "text_hash": "0edd29b7d5bdf75ce319c1a31ad38d4cb34ce340fbec17ff31ccc01a2c2faf72", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "19", "build_id": 109, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "9bbb1ef5924e4788a3dc2642828383c67ab8651fb6b0e45924c454f095b0ff47", "fragment_sha256": "3fa71c2a92e6bb54ba04b9c118ed500d056ab0fefdeb59c70eea44ee96bcb510", "source_revision": "sha256:af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:65fda1f1b62a89992b84014c9157e61b67dbe8190e93945826efec668fad038c", "translated_from_revision": "sha256:af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "body_sha256": "a2a62af01091771b8cc6e23256eae119dbb1525a212d8e3e76cd9ea9a66136fa", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/19/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 19beta4 \u00b7 using-explain", "sha256": "52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 19beta4 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/19/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 19beta4 \u00b7 using-explain", "sha256": "52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 19beta4 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em class=\"firstterm\">\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code class=\"literal\">VALUES</code> \u5b50\u53e5\u548c <code class=\"literal\">FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code class=\"command\">EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code class=\"literal\">WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a class=\"xref\" href=\"/zh/docs/19/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a class=\"xref\" href=\"/zh/docs/19/runtime-config-query.html#GUC-SEQ-PAGE-COST\">seq_page_cost</a> \u8bbe\u4e3a <code class=\"literal\">1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/19/using-explain.html#USING-EXPLAIN-BASICS\">\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "version": "19", "link_map": {"/zh/docs/19/using-explain.html#USING-EXPLAIN-BASICS": "/docs/19/using-explain.html#USING-EXPLAIN-BASICS", "/zh/docs/19/runtime-config-query.html#GUC-SEQ-PAGE-COST": "/docs/19/runtime-config-query.html#GUC-SEQ-PAGE-COST", "/zh/docs/19/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS": "/docs/19/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS"}, "body_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/19/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/19/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/19/using-explain.html#USING-EXPLAIN-BASICS\" 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": "05b8a0a99e1fd9829437f004c2a96dd9d9c7b466996bbee6b10f3f57ee757439", "content_hash": "0edd29b7d5bdf75ce319c1a31ad38d4cb34ce340fbec17ff31ccc01a2c2faf72", "source_database": "center", "source_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/19/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 19beta4 \u00b7 using-explain", "sha256": "52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 19beta4 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/19/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 19beta4 \u00b7 using-explain", "sha256": "52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 19beta4 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [{"url": "/docs/19/using-explain.html", "method": "same-major semantic node", "sha256": "7cc78f59bf29afb1811ece53e9d5c572a3f634d66d7422fb8761f19bc6811492", "language": "zh", "matched_nodes": ["#USING-EXPLAIN/div[7]/p[61]", "#USING-EXPLAIN/div[8]/p[16]"]}], "language": "zh", "original_text": {"/versions/19/description/0": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/19/facts/3/label": "Output", "/versions/19/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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": "Examples from this manual build", "/versions/19/sections/4/title": "Executor implementation notes", "/versions/19/sections/5/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation.", "/versions/19/sections/4/paragraphs/0": "Determine which direction to scan the index in based on the plan's scan direction and the current direction of execution.", "/versions/19/sections/4/paragraphs/1": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/19/sections/4/paragraphs/2": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/19/sections/4/paragraphs/3": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/19/sections/4/paragraphs/4": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/19/tables/0/columns/0/label": "Text-format label", "/versions/19/tables/0/columns/1/label": "Structured node identity", "/versions/19/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 19beta4 manual; it was not executed for this collection.", "/versions/19/sections/3/blocks/0/paragraphs/1": "In the example above, the ALL operator runs the subplan again for each row of the outer query (which accounts for the high estimated cost). Some queries can use a hashed subplan to avoid that:", "/versions/19/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 19beta4 manual; it was not executed for this collection.", "/versions/19/sections/3/blocks/1/paragraphs/1": "The \u201c Index Searches \u201d line is also useful with B-tree index scans that apply the skip scan optimization to more efficiently traverse through an index:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "44b74105d01dfae8d89b31aeb3a20c93a4b956f939500c06b8dec8f97365f4e9", "canonical_center_text_hash": "0edd29b7d5bdf75ce319c1a31ad38d4cb34ce340fbec17ff31ccc01a2c2faf72"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanInstrumentEstimate", "ExecIndexOnlyScanReInitializeDSM", "ExecIndexOnlyScanRetrieveInstrumentation"]}, "comparison_hash": "b9f4406a649452f700890bdf9ffd036b726f1aa809fe22b38dbcff8e9f5ce922", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanInstrumentEstimate", "ExecIndexOnlyScanReInitializeDSM", "ExecIndexOnlyScanRetrieveInstrumentation"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/19/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/19/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/19/using-explain.html#USING-EXPLAIN-BASICS\" 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; presentation markup normalized", "source_revision": "af105fc8e960fc836a09fc2cd7f582b49fd17675d9d36631abe3a565bfd7d701", "previous_source_revision": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}}, "20": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "715cc0348fc4d291c9e1773cc2dc6302af55b3870a92b6dbadb18ba520afc83f", "archive_sha256": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}], "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": "Index Only Scan", "identity": "Index Only 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=20", "label": "EXPLAIN"}, {"url": "/docs/devel/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/devel/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=20", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=20", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=20", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "release": {"ref": "PostgreSQL 20devel source archive", "label": "20devel", "major": "20", "channel": "devel", "revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac", "source_url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "line": 1459, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1459", "sha256": "f82f238e2e6e249e10daf2e257728494ec10de1695fcf05feaadfd7f6bf78600", "archive_sha256": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, {"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "line": 224, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:224", "sha256": "5e39b2037bed672da55104229ecc32da5abde44c26bcad01479edcfa044d09ed", "archive_sha256": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, {"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "715cc0348fc4d291c9e1773cc2dc6302af55b3870a92b6dbadb18ba520afc83f", "archive_sha256": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, {"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "aa3c27b465209c0ecd1f5e0186d39110a75ed7aafb9a196d483fccb5fc641c6b", "archive_sha256": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, {"url": "/docs/devel/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "afce066fbaecd0b7ce78ba30d776557731e46ad057c9dda332754a90e5fe59ac"}, {"url": "/docs/devel/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "afce066fbaecd0b7ce78ba30d776557731e46ad057c9dda332754a90e5fe59ac"}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/devel/using-explain.html#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "20", "build_id": 111, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "436517563e51b6d851ef143e70d01f5f68fe0a01e00a0d507e7bd79d7570aa25", "fragment_sha256": "15a78875ac0b208eff34d7bea46280d029b6e12e08fc1ea2689ddc46ed042eed", "source_revision": "sha256:49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:98c980963b401d40bd50df72b909e7523e3148b8fdb48edd897de2efb67e5235", "translated_from_revision": "sha256:49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "body_sha256": "93d9396d1ac17a03648194fc4346d237e9b65fb9f021079db733fbdbe9645b22", "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_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/devel/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 20devel \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/devel/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 20devel \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u76ee\u524d\u4e0d\u652f\u6301\u91cd\u65b0\u68c0\u67e5 ORDER BY \u8ddd\u79bb\u3002\uff08\u539f\u5219\u4e0a\uff0c\u7d22\u5f15\u82e5\u80fd\u53d6\u56de\u6700\u521d\u7d22\u5f15\u7684\u503c\uff0c\u4e5f\u5e94\u80fd\u8ba1\u7b97\u7cbe\u786e\u8ddd\u79bb\uff0c\u56e0\u6b64\u4e0d\u786e\u5b9a\u4e3a\u91cd\u65b0\u68c0\u67e5\u548c\u91cd\u65b0\u6392\u5e8f\u6dfb\u52a0\u4ee3\u7801\u662f\u5426\u503c\u5f97\u3002\u4e0d\u8fc7\u82e5\u6709\u4eba\u5c1d\u8bd5\u8fd9\u6837\u505a\uff0c\u81f3\u5c11\u5e94\u62a5\u9519\u3002\uff09", "\u5230\u8fbe\u6b64\u5904\u8868\u793a\u7d22\u5f15\u626b\u63cf\u672a\u627e\u5230\u7ed3\u679c\uff0c\u56e0\u6b64\u626b\u63cf\u5df2\u7ecf\u7ed3\u675f\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "20", "text_hash": "51a4983b248648a91d723dcdf8926f02e15f0dbeedb2a3d4aec74eaba4876720", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "20", "build_id": 111, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "436517563e51b6d851ef143e70d01f5f68fe0a01e00a0d507e7bd79d7570aa25", "fragment_sha256": "15a78875ac0b208eff34d7bea46280d029b6e12e08fc1ea2689ddc46ed042eed", "source_revision": "sha256:49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:98c980963b401d40bd50df72b909e7523e3148b8fdb48edd897de2efb67e5235", "translated_from_revision": "sha256:49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "body_sha256": "93d9396d1ac17a03648194fc4346d237e9b65fb9f021079db733fbdbe9645b22", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/devel/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 20devel \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/devel/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 20devel \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u76ee\u524d\u4e0d\u652f\u6301\u91cd\u65b0\u68c0\u67e5 ORDER BY \u8ddd\u79bb\u3002\uff08\u539f\u5219\u4e0a\uff0c\u7d22\u5f15\u82e5\u80fd\u53d6\u56de\u6700\u521d\u7d22\u5f15\u7684\u503c\uff0c\u4e5f\u5e94\u80fd\u8ba1\u7b97\u7cbe\u786e\u8ddd\u79bb\uff0c\u56e0\u6b64\u4e0d\u786e\u5b9a\u4e3a\u91cd\u65b0\u68c0\u67e5\u548c\u91cd\u65b0\u6392\u5e8f\u6dfb\u52a0\u4ee3\u7801\u662f\u5426\u503c\u5f97\u3002\u4e0d\u8fc7\u82e5\u6709\u4eba\u5c1d\u8bd5\u8fd9\u6837\u505a\uff0c\u81f3\u5c11\u5e94\u62a5\u9519\u3002\uff09", "\u5230\u8fbe\u6b64\u5904\u8868\u793a\u7d22\u5f15\u626b\u63cf\u672a\u627e\u5230\u7ed3\u679c\uff0c\u56e0\u6b64\u626b\u63cf\u5df2\u7ecf\u7ed3\u675f\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em class=\"firstterm\">\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code class=\"literal\">VALUES</code> \u5b50\u53e5\u548c <code class=\"literal\">FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code class=\"command\">EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code class=\"literal\">WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a class=\"xref\" href=\"/zh/docs/devel/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a class=\"xref\" href=\"/zh/docs/devel/runtime-config-query.html#GUC-SEQ-PAGE-COST\">seq_page_cost</a> \u8bbe\u4e3a <code class=\"literal\">1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/devel/using-explain.html#USING-EXPLAIN-BASICS\">\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "version": "20", "link_map": {"/zh/docs/devel/using-explain.html#USING-EXPLAIN-BASICS": "/docs/devel/using-explain.html#USING-EXPLAIN-BASICS", "/zh/docs/devel/runtime-config-query.html#GUC-SEQ-PAGE-COST": "/docs/devel/runtime-config-query.html#GUC-SEQ-PAGE-COST", "/zh/docs/devel/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS": "/docs/devel/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS"}, "body_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/devel/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/devel/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/devel/using-explain.html#USING-EXPLAIN-BASICS\" 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": "d8f6042b6458854b47455ccc935ed9513b3df358de8d40325eeff376792be371", "content_hash": "51a4983b248648a91d723dcdf8926f02e15f0dbeedb2a3d4aec74eaba4876720", "source_database": "center", "source_revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/devel/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 20devel \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/devel/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 20devel \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u76ee\u524d\u4e0d\u652f\u6301\u91cd\u65b0\u68c0\u67e5 ORDER BY \u8ddd\u79bb\u3002\uff08\u539f\u5219\u4e0a\uff0c\u7d22\u5f15\u82e5\u80fd\u53d6\u56de\u6700\u521d\u7d22\u5f15\u7684\u503c\uff0c\u4e5f\u5e94\u80fd\u8ba1\u7b97\u7cbe\u786e\u8ddd\u79bb\uff0c\u56e0\u6b64\u4e0d\u786e\u5b9a\u4e3a\u91cd\u65b0\u68c0\u67e5\u548c\u91cd\u65b0\u6392\u5e8f\u6dfb\u52a0\u4ee3\u7801\u662f\u5426\u503c\u5f97\u3002\u4e0d\u8fc7\u82e5\u6709\u4eba\u5c1d\u8bd5\u8fd9\u6837\u505a\uff0c\u81f3\u5c11\u5e94\u62a5\u9519\u3002\uff09", "\u5230\u8fbe\u6b64\u5904\u8868\u793a\u7d22\u5f15\u626b\u63cf\u672a\u627e\u5230\u7ed3\u679c\uff0c\u56e0\u6b64\u626b\u63cf\u5df2\u7ecf\u7ed3\u675f\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [{"url": "/docs/devel/using-explain.html", "method": "same-major semantic node", "sha256": "2744ee0e88d132c504bf5e102765edaabd393eb12c59294093db6d90b26dd65c", "language": "zh", "matched_nodes": ["#USING-EXPLAIN/div[7]/p[61]", "#USING-EXPLAIN/div[8]/p[16]"]}], "language": "zh", "original_text": {"/summary": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/category": "Scan", "/versions/20/description/0": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/20/facts/3/label": "Output", "/versions/20/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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": "Examples from this manual build", "/versions/20/sections/4/title": "Executor implementation notes", "/versions/20/sections/5/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation.", "/versions/20/sections/4/paragraphs/0": "Determine which direction to scan the index in based on the plan's scan direction and the current direction of execution.", "/versions/20/sections/4/paragraphs/1": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/20/sections/4/paragraphs/2": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/20/sections/4/paragraphs/3": "We don't currently support rechecking ORDER BY distances. (In principle, if the index can support retrieval of the originally indexed value, it should be able to produce an exact distance calculation too. So it's not clear that adding code here for recheck/re-sort would be worth the trouble. But we should at least throw an error if someone tries it.)", "/versions/20/sections/4/paragraphs/4": "if we get here it means the index scan failed so we are at the end of the scan..", "/versions/20/tables/0/columns/0/label": "Text-format label", "/versions/20/tables/0/columns/1/label": "Structured node identity", "/versions/20/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 20devel manual; it was not executed for this collection.", "/versions/20/sections/3/blocks/0/paragraphs/1": "In the example above, the ALL operator runs the subplan again for each row of the outer query (which accounts for the high estimated cost). Some queries can use a hashed subplan to avoid that:", "/versions/20/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 20devel manual; it was not executed for this collection.", "/versions/20/sections/3/blocks/1/paragraphs/1": "The \u201c Index Searches \u201d line is also useful with B-tree index scans that apply the skip scan optimization to more efficiently traverse through an index:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "cd63c45abb578808dbd295409f221455068359fd0b5927ef08c35ebad88fe0b8", "canonical_center_text_hash": "51a4983b248648a91d723dcdf8926f02e15f0dbeedb2a3d4aec74eaba4876720"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanInstrumentEstimate", "ExecIndexOnlyScanReInitializeDSM", "ExecIndexOnlyScanRetrieveInstrumentation"]}, "comparison_hash": "b9f4406a649452f700890bdf9ffd036b726f1aa809fe22b38dbcff8e9f5ce922", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanInstrumentEstimate", "ExecIndexOnlyScanReInitializeDSM", "ExecIndexOnlyScanRetrieveInstrumentation"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanInstrumentEstimate, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/devel/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/devel/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/devel/using-explain.html#USING-EXPLAIN-BASICS\" 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; presentation markup normalized", "source_revision": "49c73aa4c9cacef8ca979276a28ac416c08e9e54c9baee4ae5fd116a35fa13ac", "previous_source_revision": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}}}}, "snapshot": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "357d4ddbd6ba5d9b02f04185e579e2f2dc889d0d94875580770c8649cc427e6d", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}], "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": "Index Only Scan", "identity": "Index Only 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"}, {"url": "/wiki/guc/enable_indexonlyscan/?v=18", "label": "enable_indexonlyscan"}, {"url": "/wiki/guc/random_page_cost/?v=18", "label": "random_page_cost"}, {"url": "/wiki/indexam/?v=18", "label": "\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5"}], "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": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "line": 1447, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1447", "sha256": "34c86d6070224a0e981efef51f79101d6d505e5874f1684ace183034bab14bb4", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "line": 224, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:224", "sha256": "f8a06a3f539077249b20664b2812433db6d7bd12b2c0ca633525db43d06f112a", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/backend/executor/nodeIndexonlyscan.c", "label": "src/backend/executor/nodeIndexonlyscan.c", "sha256": "357d4ddbd6ba5d9b02f04185e579e2f2dc889d0d94875580770c8649cc427e6d", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "52422b327a8049fbbb20d8b96008a0fc0a6fafa60f7eff3c695d5b2e83830120", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, {"url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}], "zh_from": {"kind": "same-version-chinese-manual-with-authored-translation-of-reviewed-guidance", "manual": {"url": "/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "18", "build_id": 107, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "d2f749744b3ac5aa2eb0154f295e8163903cd20fcc130c74c6172cdf2ae3a9df", "fragment_sha256": "bc79b6f9c70f2b56968e08ea26d2c9ec3d395e425aca0594e227203daa0ad29b", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b", "translated_from_revision": null}, "body_sha256": "92dd757c4d84eb6e5a87e99db3bdc8fc9cb7eca771a3337aeb2b28c22032b6e7", "runtime_rerun": false, "authored_translation": "authored-translation-of-reviewed-guidance", "source_facts_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "facts_zh": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "node_tag": "T_IndexOnlyScan", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "center_zh": {"title": "IndexOnlyScan", "locale": "zh-Hans", "source": {"key": "index-only-scan", "locale": "zh-Hans", "version": "18", "text_hash": "981a46151f5f56f4097f6d59815dc1618177e9984f6f208be3e5bfa55f861349", "collection": "plan", "dataset_hash": "7c31b524dfe136022d39a6ae8dcfac6b3bbd5f8fdaf422536599981252aff0c9", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "payload": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_IndexOnlyScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Index Only Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15\u3001\u5173\u7cfb\u53ca\u53ef\u89c1\u6027\u4fe1\u606f"}, {"label": "\u8f93\u51fa", "value": "\u6765\u81ea\u7d22\u5f15\u503c\u4e14\u6ee1\u8db3\u6761\u4ef6\u7684\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitIndexOnlyScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "tables": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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#USING-EXPLAIN-BASICS", "anchor": "USING-EXPLAIN-BASICS", "locale": "zh-Hans", "version": "18", "build_id": 107, "page_key": "using-explain.html", "extraction": "concept-introduction", "source_hash": "d2f749744b3ac5aa2eb0154f295e8163903cd20fcc130c74c6172cdf2ae3a9df", "fragment_sha256": "bc79b6f9c70f2b56968e08ea26d2c9ec3d395e425aca0594e227203daa0ad29b", "source_revision": "unknown:rendered-translation-baseline", "translation_revision": "git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b", "translated_from_revision": null}, "body_sha256": "92dd757c4d84eb6e5a87e99db3bdc8fc9cb7eca771a3337aeb2b28c22032b6e7", "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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em class=\"firstterm\">\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code class=\"literal\">VALUES</code> \u5b50\u53e5\u548c <code class=\"literal\">FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code class=\"command\">EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code class=\"literal\">WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a class=\"xref\" href=\"/zh/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a class=\"xref\" href=\"/zh/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST\">seq_page_cost</a> \u8bbe\u4e3a <code class=\"literal\">1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS\">\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": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "version": "18", "link_map": {"/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "/zh/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST": "/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST", "/zh/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS": "/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS"}, "body_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS\" 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": "6562a9408ebc53c582c49aa54c6caea0900f02cb51edee4901e1e9e374a14c70", "content_hash": "981a46151f5f56f4097f6d59815dc1618177e9984f6f208be3e5bfa55f861349", "source_database": "center", "source_revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "tables_zh": [{"key": "explain-labels", "rows": [{"label": "Index Only Scan", "identity": "Index Only 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": ["\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\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\uff1aIndex Only 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\uff1aExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT *\nFROM tenk1 t\nWHERE t.unique1 NOT IN (SELECT o.unique1 FROM onek o);\n\n                                         QUERY PLAN\n--------------------------------------------------------------------------------------------\n Seq Scan on tenk1 t  (cost=61.77..531.77 rows=5000 width=244)\n   Filter: (NOT (ANY (unique1 = (hashed SubPlan 1).col1)))\n   SubPlan 1\n     ->  Index Only Scan using onek_unique1 on onek o  (cost=0.28..59.27 rows=1000 width=4)\n(4 rows)", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c ALL \u64cd\u4f5c\u7b26\u4f1a\u5bf9\u5916\u5c42\u67e5\u8be2\u7684\u6bcf\u4e00\u884c\u90fd\u91cd\u65b0\u6267\u884c\u4e00\u6b21\u5b50\u8ba1\u5212\uff08\u8fd9\u4e5f\u662f\u4f30\u8ba1\u4ee3\u4ef7\u5f88\u9ad8\u7684\u539f\u56e0\uff09\u3002\u6709\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528 hash \u5b50\u8ba1\u5212 \u6765\u907f\u514d\u8fd9\u4e00\u70b9\uff1a"]}, {"code": "EXPLAIN ANALYZE SELECT four, unique1 FROM tenk1 WHERE four BETWEEN 1 AND 3 AND unique1 = 42;\n                                                              QUERY PLAN\n----------------------------------------------------------------------------------------------------------------------------------\n Index Only Scan using tenk1_four_unique1_idx on tenk1  (cost=0.29..6.90 rows=1 width=8) (actual time=0.006..0.007 rows=1.00 loops=1)\n   Index Cond: ((four >= 1) AND (four <= 3) AND (unique1 = 42))\n   Heap Fetches: 0\n   Index Searches: 3\n   Buffers: shared hit=7\n Planning Time: 0.029 ms\n Execution Time: 0.012 ms", "source": {"url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 18.6 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u201c Index Searches \u201d \u8fd9\u4e00\u884c\u5bf9\u4e8e\u5e94\u7528\u4e86 \u8df3\u8fc7\u626b\u63cf \uff08skip scan\uff09\u4f18\u5316\u3001\u4ee5\u66f4\u9ad8\u6548\u65b9\u5f0f\u904d\u5386\u7d22\u5f15\u7684 B-\u6811\u7d22\u5f15\u626b\u63cf\u540c\u6837\u6709\u7528\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["\u6839\u636e\u8ba1\u5212\u7684\u626b\u63cf\u65b9\u5411\u548c\u5f53\u524d\u6267\u884c\u65b9\u5411\uff0c\u786e\u5b9a\u7d22\u5f15\u626b\u63cf\u65b9\u5411\u3002", "\u4ec5\u7d22\u5f15\u626b\u63cf\u4e0d\u5e76\u884c\u6267\u884c\uff0c\u6216\u539f\u8ba1\u5212\u5e76\u884c\u7684\u4ec5\u7d22\u5f15\u626b\u63cf\u4ee5\u4e32\u884c\u65b9\u5f0f\u6267\u884c\u65f6\uff0c\u4f1a\u5230\u8fbe\u6b64\u5904\u3002", "\u5982\u679c\u6ca1\u6709\u9700\u8981\u8ba1\u7b97\u7684\u8fd0\u884c\u65f6\u952e\uff0c\u6216\u8fd0\u884c\u65f6\u952e\u5df2\u51c6\u5907\u5c31\u7eea\uff0c\u5219\u5c06\u626b\u63cf\u952e\u4f20\u7ed9\u7d22\u5f15\u8bbf\u95ee\u65b9\u6cd5\u3002", "\u82e5 TID \u6307\u5411\u7684\u5806\u9875\u9762\u4e0a\u6240\u6709\u5143\u7ec4\u90fd\u5df2\u77e5\u5bf9\u6240\u6709\u4e8b\u52a1\u53ef\u89c1\uff0c\u5c31\u53ef\u4ee5\u8df3\u8fc7\u5806\u8bfb\u53d6\u3002\u65e0\u8bba\u662f\u5426\u8bfb\u53d6\u5806\uff0c\u90fd\u4f7f\u7528\u7d22\u5f15\u5143\u7ec4\u800c\u975e\u5806\u5143\u7ec4\u4f5c\u4e3a\u6570\u636e\u6765\u6e90\u3002", "\u5173\u4e8e\u5185\u5b58\u5e8f\uff1avisibilitymap_get_status \u4e0d\u9501\u5b9a\u53ef\u89c1\u6027\u6620\u5c04\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u6b64\u5904\u8bfb\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u7a0d\u6709\u6ede\u540e\uff0c\u4f46\u4e0d\u4f1a\u6ede\u540e\u5230\u5f71\u54cd\u6b63\u786e\u6027\u3002"]}, {"code": "case T_IndexOnlyScan:\n\t\t\tpname = sname = \"Index Only Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "localization": {"status": "complete", "sources": [{"url": "/docs/18/using-explain.html", "method": "same-major semantic node", "sha256": "b8835ec9adbc70ec150667a6b5443f8d298222dc0cc8c2bd1abb1c1d64895904", "language": "zh", "matched_nodes": ["#USING-EXPLAIN/div[7]/p[61]", "#USING-EXPLAIN/div[8]/p[13]"]}], "language": "zh", "original_text": {"/versions/18/description/0": "Uses index values for the result and checks tuple visibility, visiting the heap when the visibility map does not suffice.", "/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": "An index, relation and visibility information", "/versions/18/facts/3/label": "Output", "/versions/18/facts/3/value": "Qualified tuples from index values", "/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/related/5/label": "Index AM", "/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": "Examples from this manual build", "/versions/18/sections/4/title": "Executor implementation notes", "/versions/18/sections/5/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: Index Only 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: ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation.", "/versions/18/sections/4/paragraphs/0": "Determine which direction to scan the index in based on the plan's scan direction and the current direction of execution.", "/versions/18/sections/4/paragraphs/1": "We reach here if the index only scan is not parallel, or if we're serially executing an index only scan that was planned to be parallel.", "/versions/18/sections/4/paragraphs/2": "If no run-time keys to calculate or they are ready, go ahead and pass the scankeys to the index AM.", "/versions/18/sections/4/paragraphs/3": "We can skip the heap fetch if the TID references a heap page on which all tuples are known visible to everybody. In any case, we'll use the index tuple not the heap tuple as the data source.", "/versions/18/sections/4/paragraphs/4": "Note on Memory Ordering Effects: visibilitymap_get_status does not lock the visibility map buffer, and therefore the result we read here could be slightly stale. However, it can't be stale enough to matter.", "/versions/18/tables/0/columns/0/label": "Text-format label", "/versions/18/tables/0/columns/1/label": "Structured node identity", "/versions/18/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 18.6 manual; it was not executed for this collection.", "/versions/18/sections/3/blocks/0/paragraphs/1": "In the example above, the ALL operator runs the subplan again for each row of the outer query (which accounts for the high estimated cost). Some queries can use a hashed subplan to avoid that:", "/versions/18/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 18.6 manual; it was not executed for this collection.", "/versions/18/sections/3/blocks/1/paragraphs/1": "The \u201c Index Searches \u201d line is also useful with B-tree index scans that apply the skip scan optimization to more efficiently traverse through an index:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "0df59264ee459ceab9eafca048e06d3457cabcc265927bfcb60321745ce7cf40", "canonical_center_text_hash": "981a46151f5f56f4097f6d59815dc1618177e9984f6f208be3e5bfa55f861349"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "description_zh": "\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002", "comparison_data": {"node_tag": "T_IndexOnlyScan", "strategies": [], "text_names": ["Index Only Scan"], "initializer": "ExecInitIndexOnlyScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM", "ExecIndexOnlyScanRetrieveInstrumentation"]}, "comparison_hash": "149a13d2842f396b0e35eb23a93337d9e8c708fbcf6665eec0ab0ebbd5320b9b", "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/nodeIndexonlyscan.c"}, "parallel_callbacks": ["ExecIndexOnlyScanEstimate", "ExecIndexOnlyScanInitializeDSM", "ExecIndexOnlyScanInitializeWorker", "ExecIndexOnlyScanReInitializeDSM", "ExecIndexOnlyScanRetrieveInstrumentation"], "description_zh_html": "<p>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/zh/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\" rel=\"nofollow\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/zh/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST\" rel=\"nofollow\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/zh/docs/18/using-explain.html#USING-EXPLAIN-BASICS\" 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>\u5229\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u65ad\u65f6\u4ecd\u8bbf\u95ee\u5806\u3002</p><p>\u6838\u5fc3\u8282\u70b9\u6807\u8bc6\uff1a<code>T_IndexOnlyScan</code>\uff1bEXPLAIN \u540d\u79f0\uff1a<code>Index Only Scan</code>\u3002</p><p>\u672c\u7248\u672c\u6e90\u7801\u4e2d\u7684\u5e76\u884c\u6267\u884c\u6216\u89c2\u6d4b\u56de\u8c03\uff1a<code>ExecIndexOnlyScanEstimate, ExecIndexOnlyScanInitializeDSM, ExecIndexOnlyScanInitializeWorker, ExecIndexOnlyScanReInitializeDSM, ExecIndexOnlyScanRetrieveInstrumentation</code>\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    \u67e5\u8be2\u8ba1\u5212\u7684\u7ed3\u6784\u662f\u4e00\u68f5\u7531<em>\u8ba1\u5212\u8282\u70b9</em>\u7ec4\u6210\u7684\u6811\u3002\u6811\u7684\u6700\u5e95\u5c42\u662f\u626b\u63cf\u8282\u70b9\uff0c\u5b83\u4eec\u4ece\u8868\u4e2d\u8fd4\u56de\u539f\u59cb\u884c\u3002\u4e0d\u540c\u7684\u8868\u8bbf\u95ee\u65b9\u6cd5\u5bf9\u5e94\u4e0d\u540c\u7c7b\u578b\u7684\u626b\u63cf\u8282\u70b9\uff0c\u4f8b\u5982\u987a\u5e8f\u626b\u63cf\u3001\u7d22\u5f15\u626b\u63cf\u548c\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u3002\u4e5f\u6709\u4e00\u4e9b\u5e76\u975e\u8868\u7684\u884c\u6765\u6e90\uff0c\u4f8b\u5982 <code>VALUES</code> \u5b50\u53e5\u548c <code>FROM</code> \u4e2d\u7684\u8fd4\u56de\u96c6\u5408\u51fd\u6570\uff0c\u5b83\u4eec\u4e5f\u5404\u81ea\u6709\u5bf9\u5e94\u7684\u626b\u63cf\u8282\u70b9\u7c7b\u578b\u3002\u5982\u679c\u67e5\u8be2\u9700\u8981\u5bf9\u539f\u59cb\u884c\u6267\u884c\u8fde\u63a5\u3001\u805a\u5408\u3001\u6392\u5e8f\u6216\u5176\u4ed6\u64cd\u4f5c\uff0c\u90a3\u4e48\u626b\u63cf\u8282\u70b9\u4e4b\u4e0a\u8fd8\u4f1a\u51fa\u73b0\u989d\u5916\u7684\u8282\u70b9\u6765\u5b8c\u6210\u8fd9\u4e9b\u64cd\u4f5c\u3002\u540c\u6837\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u901a\u5e38\u4e0d\u6b62\u4e00\u79cd\u5b9e\u73b0\u65b9\u5f0f\uff0c\u56e0\u6b64\u8fd9\u91cc\u4e5f\u4f1a\u51fa\u73b0\u4e0d\u540c\u7684\u8282\u70b9\u7c7b\u578b\u3002<code>EXPLAIN</code> \u4f1a\u4e3a\u8ba1\u5212\u6811\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u8f93\u51fa\u4e00\u884c\uff0c\u663e\u793a\u57fa\u672c\u8282\u70b9\u7c7b\u578b\u4ee5\u53ca\u89c4\u5212\u5668\u5bf9\u8be5\u8ba1\u5212\u8282\u70b9\u6267\u884c\u4ee3\u4ef7\u7684\u4f30\u8ba1\u503c\u3002\u8fd8\u53ef\u80fd\u51fa\u73b0\u76f8\u5bf9\u8282\u70b9\u6458\u8981\u884c\u7f29\u8fdb\u7684\u9644\u52a0\u884c\uff0c\u7528\u6765\u663e\u793a\u8be5\u8282\u70b9\u7684\u66f4\u591a\u5c5e\u6027\u3002\u7b2c\u4e00\u884c\uff0c\u4e5f\u5c31\u662f\u6700\u9876\u5c42\u8282\u70b9\u7684\u6458\u8981\u884c\uff0c\u7ed9\u51fa\u4e86\u6574\u4e2a\u8ba1\u5212\u7684\u4f30\u8ba1\u603b\u6267\u884c\u4ee3\u4ef7\uff1b\u89c4\u5212\u5668\u529b\u56fe\u6700\u5c0f\u5316\u7684\u6b63\u662f\u8fd9\u4e2a\u6570\u5b57\u3002\n   </p><p>\n    \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u793a\u4f8b\uff0c\u4ec5\u7528\u4e8e\u5c55\u793a\u8f93\u51fa\u7684\u6837\u5b50\uff1a\n\n</p><p>\n    \u7531\u4e8e\u8fd9\u4e2a\u67e5\u8be2\u6ca1\u6709 <code>WHERE</code> \u5b50\u53e5\uff0c\u5b83\u5fc5\u987b\u626b\u63cf\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u56e0\u6b64\u89c4\u5212\u5668\u9009\u62e9\u4e86\u4e00\u4e2a\u7b80\u5355\u7684\u987a\u5e8f\u626b\u63cf\u8ba1\u5212\u3002\u5706\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u8868\u793a\uff1a\n\n    </p><p>\n    \u8fd9\u4e9b\u4ee3\u4ef7\u4f7f\u7528\u7531\u89c4\u5212\u5668\u4ee3\u4ef7\u53c2\u6570\u51b3\u5b9a\u7684\u4efb\u610f\u5355\u4f4d\u6765\u8861\u91cf\uff08\u89c1<a href=\"/docs/18/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS\">\u7b2c\u00a019.7.2\u00a0\u8282</a>\uff09\u3002\u4f20\u7edf\u4e0a\u901a\u5e38\u4ee5\u78c1\u76d8\u9875\u8bfb\u53d6\u4f5c\u4e3a\u4ee3\u4ef7\u5355\u4f4d\uff1b\u4e5f\u5c31\u662f\u8bf4\uff0c\u60ef\u4f8b\u4e0a\u5c06 <a href=\"/docs/18/runtime-config-query.html#GUC-SEQ-PAGE-COST\">seq_page_cost</a> \u8bbe\u4e3a <code>1.0</code>\uff0c\u5176\u4ed6\u4ee3\u4ef7\u53c2\u6570\u90fd\u76f8\u5bf9\u5b83\u6765\u8bbe\u5b9a\u3002\u672c\u8282\u4e2d\u7684\u793a\u4f8b\u90fd\u4f7f\u7528\u9ed8\u8ba4\u4ee3\u4ef7\u53c2\u6570\u3002\n   </p><p><a href=\"/docs/18/using-explain.html#USING-EXPLAIN-BASICS\">\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": "changed", "diff": "--- PostgreSQL 17\n+++ PostgreSQL 18\n@@ -6,7 +6,8 @@\n     \"ExecIndexOnlyScanEstimate\",\n     \"ExecIndexOnlyScanInitializeDSM\",\n     \"ExecIndexOnlyScanInitializeWorker\",\n-    \"ExecIndexOnlyScanReInitializeDSM\"\n+    \"ExecIndexOnlyScanReInitializeDSM\",\n+    \"ExecIndexOnlyScanRetrieveInstrumentation\"\n   ],\n   \"partial_modes\": [],\n   \"strategies\": [],"}}