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["\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"}], "strategies": [], "description": 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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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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": 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"\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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "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": "\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", "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"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "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": "\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", "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"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "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": "\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", "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"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "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": "\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", "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"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "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": "\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", "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"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "explain_prefixes": ["Parallel", "Async"], "runtime_verified": false, "source_inventory": {"explain": 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"\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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "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": "\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", "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": "https://pg.center/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed", "language": "en", "original_url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS"}, {"url": "https://pg.center/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed", "language": "en", "original_url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "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": "\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", "source_notes": []}, "tables": [{"key": "explain-labels", 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"src/backend/executor/nodeIndexonlyscan.c", "sha256": "882faa33a186834d3dd5f72fdc337441da4d39515ad02b672d5ca3c140b111cb", "archive_sha256": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}, {"url": "https://ftp.postgresql.org/pub/source/v19beta4/postgresql-19beta4.tar.bz2", "path": "src/include/nodes/plannodes.h", "label": "src/include/nodes/plannodes.h", "sha256": "1c65d5d6b6c81c71531685843647869bcae630779d815a5036b06e070c6c06c7", "archive_sha256": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}, {"url": "https://pg.center/docs/19/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 19beta4 \u00b7 using-explain", "sha256": "52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b", "language": "en", "original_url": "/docs/19/using-explain.html#USING-EXPLAIN-BASICS"}, {"url": "https://pg.center/docs/19/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 19beta4 \u00b7 using-explain", "sha256": "52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b", "language": "en", "original_url": "/docs/19/using-explain.html#USING-EXPLAIN-ANALYZE"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "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": "\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", "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": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41", "source_url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "source_snapshot_utc": "26-Sep-2026 20:22"}, "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": "13402758013520451539427b5993db06d463ca11c4e2d4cc5444e82367688077", "archive_sha256": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}, {"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": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}, {"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"}, {"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": "7a94ed1652f0d74d50c39971d1cd3e8051dbc0d6058f31b6de71a433ca343521", "archive_sha256": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}, {"url": "https://pg.center/docs/devel/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31", "language": "en", "original_url": "/docs/devel/using-explain.html#USING-EXPLAIN-BASICS"}, {"url": "https://pg.center/docs/devel/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 20devel \u00b7 using-explain", "sha256": "99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31", "language": "en", "original_url": "/docs/devel/using-explain.html#USING-EXPLAIN-ANALYZE"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}}}, "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": 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"\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", "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": "https://pg.center/docs/18/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed", "language": "en", "original_url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS"}, {"url": "https://pg.center/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE", "path": "using-explain.html", "label": "PostgreSQL 18.6 \u00b7 using-explain", "sha256": "60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed", "language": "en", "original_url": "/docs/18/using-explain.html#USING-EXPLAIN-ANALYZE"}], "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"}], "strategies": [], "description": ["\u4f7f\u7528\u7d22\u5f15\u503c\u751f\u6210\u7ed3\u679c\u5e76\u68c0\u67e5\u5143\u7ec4\u53ef\u89c1\u6027\uff1b\u53ef\u89c1\u6027\u6620\u5c04\u4e0d\u8db3\u4ee5\u5224\u5b9a\u65f6\u8bbf\u95ee\u5806\u3002"], "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"}, "evidence_kind": "source and documentation", "explain_names": ["Index Only Scan"], "partial_modes": [], "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", "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"]}, "comparison": {"left": "18", "right": "19", "status": "changed", "diff": "--- PostgreSQL 18\n+++ PostgreSQL 19\n@@ -6,6 +6,7 @@\n     \"ExecIndexOnlyScanEstimate\",\n     \"ExecIndexOnlyScanInitializeDSM\",\n     \"ExecIndexOnlyScanInitializeWorker\",\n+    \"ExecIndexOnlyScanInstrumentEstimate\",\n     \"ExecIndexOnlyScanReInitializeDSM\",\n     \"ExecIndexOnlyScanRetrieveInstrumentation\"\n   ],"}}