{"kind": "plan", "major": "18", "item": {"slug": "bitmap-index-scan", "name": "Bitmap Index Scan", "name_zh": "BitmapIndexScan", "category": "\u4f4d\u56fe", "summary": "\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002", "aliases": ["Bitmap Index Scan", "BitmapIndexScan", "T_BitmapIndexScan"], "content_hash": "95f74ec181241e03fbb7332f001e6b93b8586d62da8b2505dfa1919acfa40ddd", "versions": {"10": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_BitmapIndexScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Bitmap Index Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15"}, {"label": "\u8f93\u51fa", "value": "\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\uff0c\u4e0d\u662f\u5143\u7ec4\u6d41"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "0a18120b59b87f6139bb2c67de548494d5d0ad6ab03533e53ff267db30196068", "archive_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, {"url": "https://ftp.postgresql.org/pub/source/v10.23/postgresql-10.23.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "66152ac93c470e2705adfef9a4c10ad3aa1beccb7baccf0b16dd96f3d59a0ec0", "archive_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem 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"src/backend/nodes/tidbitmap.c", "sha256": "66152ac93c470e2705adfef9a4c10ad3aa1beccb7baccf0b16dd96f3d59a0ec0", "archive_sha256": "94a4b2528372458e5662c18d406629266667c437198160a18cdfd2c4a4d6eee9"}, {"url": "https://pg.center/docs/10/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 10.23 \u00b7 using-explain", "sha256": "a4b4304aedb0a2da0145cc7c35b03b319a5c7ee3df35a8ef84ab6d3a610f98f3", "language": "en", "original_url": "/docs/10/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.07..229.20 rows=101 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/10/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 10.23 \u00b7 using-explain", "sha256": "a4b4304aedb0a2da0145cc7c35b03b319a5c7ee3df35a8ef84ab6d3a610f98f3"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 10.23 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..229.43 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/10/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 10.23 \u00b7 using-explain", "sha256": "a4b4304aedb0a2da0145cc7c35b03b319a5c7ee3df35a8ef84ab6d3a610f98f3"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 10.23 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002"], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/10/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/versions/10/facts/0/label": "Core node tag", "/versions/10/facts/1/label": "Structured EXPLAIN Node Type", "/versions/10/facts/2/label": "Inputs", "/versions/10/facts/2/value": "An index", "/versions/10/facts/3/label": "Output", "/versions/10/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/versions/10/facts/4/label": "Executor initializer", "/versions/10/facts/5/label": "Memory mechanism", "/versions/10/tables/0/title": "EXPLAIN labels in this source build", "/versions/10/related/1/label": "Using EXPLAIN", "/versions/10/related/2/label": "Parallel plans", "/versions/10/related/5/label": "Index AM", "/versions/10/sections/0/title": "EXPLAIN names and attributes", "/versions/10/sections/1/title": "Memory and temporary storage", "/versions/10/sections/2/title": "Parallel execution and instrumentation", "/versions/10/sections/3/title": "Examples from this manual build", "/versions/10/sections/4/title": "Executor implementation notes", "/versions/10/sections/5/title": "EXPLAIN identity in core source", "/versions/10/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/versions/10/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/10/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/10/sections/4/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/10/sections/4/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/10/sections/4/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/10/sections/4/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/10/sections/4/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/10/tables/0/columns/0/label": "Text-format label", "/versions/10/tables/0/columns/1/label": "Structured node identity", "/versions/10/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 10.23 manual; it was not executed for this collection.", "/versions/10/sections/3/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/10/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 10.23 manual; it was not executed for this collection.", "/versions/10/sections/3/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "cf7ea12132345006e44c92c99addf03bc0847a2b6117baf52b8c465466f86107"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "181aa05754bb5e78dc6e3dca3e202c115ae152e237511ac01e048514a8036ded", "archive_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, {"url": "https://ftp.postgresql.org/pub/source/v11.22/postgresql-11.22.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "a47e915ced1ae75d21b8d7b7b67ae09c4bf230069208aa5d9f5b6c2ca6ae85d1", "archive_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem 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"src/backend/nodes/tidbitmap.c", "sha256": "a47e915ced1ae75d21b8d7b7b67ae09c4bf230069208aa5d9f5b6c2ca6ae85d1", "archive_sha256": "2cb7c97d7a0d7278851bbc9c61f467b69c094c72b81740b751108e7892ebe1f0"}, {"url": "https://pg.center/docs/11/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 11.22 \u00b7 using-explain", "sha256": "8411bc78085d4737e32d7cca103d859da6c6539e33ec5e2fba46e74c6f199d8a", "language": "en", "original_url": "/docs/11/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.07..229.20 rows=101 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/11/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 11.22 \u00b7 using-explain", "sha256": "8411bc78085d4737e32d7cca103d859da6c6539e33ec5e2fba46e74c6f199d8a"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 11.22 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..229.43 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/11/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 11.22 \u00b7 using-explain", "sha256": "8411bc78085d4737e32d7cca103d859da6c6539e33ec5e2fba46e74c6f199d8a"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 11.22 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002"], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/11/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/11/facts/3/label": "Output", "/versions/11/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Examples from this manual build", "/versions/11/sections/4/title": "Executor implementation notes", "/versions/11/sections/5/title": "EXPLAIN identity in core source", "/versions/11/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/versions/11/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/11/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/11/sections/4/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/11/sections/4/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/11/sections/4/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/11/sections/4/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/11/sections/4/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/11/tables/0/columns/0/label": "Text-format label", "/versions/11/tables/0/columns/1/label": "Structured node identity", "/versions/11/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 11.22 manual; it was not executed for this collection.", "/versions/11/sections/3/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/11/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 11.22 manual; it was not executed for this collection.", "/versions/11/sections/3/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "9d907117f5e4e14d35b68595a3e9386da60951193be52cbb9b4c61ebd4ad447f"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "7fe85640bde0b6f74d609c1d443f5622ea6d7dc2d77e2a92cd6fdf51a572ae64", "archive_sha256": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, {"url": "https://ftp.postgresql.org/pub/source/v12.22/postgresql-12.22.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "8a18d2e770adab40a9172ebc6895501ec22f650b479c4e9ce44ca010c57ad24d", "archive_sha256": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem 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"src/backend/nodes/tidbitmap.c", "sha256": "8a18d2e770adab40a9172ebc6895501ec22f650b479c4e9ce44ca010c57ad24d", "archive_sha256": "8df3c0474782589d3c6f374b5133b1bd14d168086edbc13c6e72e67dd4527a3b"}, {"url": "https://pg.center/docs/12/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 12.22 \u00b7 using-explain", "sha256": "06297525f2180b07e752837a3351be9c871b56559f535bcd0a67dec9baac10c0", "language": "en", "original_url": "/docs/12/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.07..229.20 rows=101 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/12/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 12.22 \u00b7 using-explain", "sha256": "06297525f2180b07e752837a3351be9c871b56559f535bcd0a67dec9baac10c0"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 12.22 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..229.43 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/12/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 12.22 \u00b7 using-explain", "sha256": "06297525f2180b07e752837a3351be9c871b56559f535bcd0a67dec9baac10c0"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 12.22 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002"], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/12/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/12/facts/3/label": "Output", "/versions/12/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Examples from this manual build", "/versions/12/sections/4/title": "Executor implementation notes", "/versions/12/sections/5/title": "EXPLAIN identity in core source", "/versions/12/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/versions/12/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/12/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/12/sections/4/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/12/sections/4/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/12/sections/4/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/12/sections/4/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/12/sections/4/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/12/tables/0/columns/0/label": "Text-format label", "/versions/12/tables/0/columns/1/label": "Structured node identity", "/versions/12/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 12.22 manual; it was not executed for this collection.", "/versions/12/sections/3/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/12/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 12.22 manual; it was not executed for this collection.", "/versions/12/sections/3/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "62d641420f04c137ae44d41b7c276f1fc0df749826ffd0370a6a7f33a0733381"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v13.23/postgresql-13.23.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "bed645648d6c8ab8ba338b23d5b6bf1bd22bed1a3f7d72db0397d526339c4073", "archive_sha256": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, {"url": "https://ftp.postgresql.org/pub/source/v13.23/postgresql-13.23.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "a0823f106dd0af7415c44a788a8b258dc13afc6dab320d0dec0a2d17f418fdb8", "archive_sha256": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem 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"src/backend/nodes/tidbitmap.c", "sha256": "a0823f106dd0af7415c44a788a8b258dc13afc6dab320d0dec0a2d17f418fdb8", "archive_sha256": "6ec3c82726af92b7dec873fa1cdf881eca92a4219787dfad05acb6b10e041fd6"}, {"url": "https://pg.center/docs/13/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 13.23 \u00b7 using-explain", "sha256": "650fd8629382d5dc8f9f8412c50ec5f32442a9ad2f98ca88e5348a7c2bd0ac7a", "language": "en", "original_url": "/docs/13/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index Scan.", 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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\uff1anone extracted from this node implementation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.07..229.20 rows=101 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/13/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 13.23 \u00b7 using-explain", "sha256": "650fd8629382d5dc8f9f8412c50ec5f32442a9ad2f98ca88e5348a7c2bd0ac7a"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 13.23 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..229.43 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/13/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 13.23 \u00b7 using-explain", "sha256": "650fd8629382d5dc8f9f8412c50ec5f32442a9ad2f98ca88e5348a7c2bd0ac7a"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 13.23 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002"], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/13/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/13/facts/3/label": "Output", "/versions/13/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Examples from this manual build", "/versions/13/sections/4/title": "Executor implementation notes", "/versions/13/sections/5/title": "EXPLAIN identity in core source", "/versions/13/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/versions/13/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/13/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/13/sections/4/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/13/sections/4/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/13/sections/4/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/13/sections/4/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/13/sections/4/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/13/tables/0/columns/0/label": "Text-format label", "/versions/13/tables/0/columns/1/label": "Structured node identity", "/versions/13/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 13.23 manual; it was not executed for this collection.", "/versions/13/sections/3/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/13/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 13.23 manual; it was not executed for this collection.", "/versions/13/sections/3/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "4aea4090751e7a77e79730f1522396b4e42ccae27c3189322112dce1b4b18495"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "ed88a656eb113183830b115dc514d98401e2163a56ae54c911c381f8d0ad012c", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, {"url": "https://ftp.postgresql.org/pub/source/v14.24/postgresql-14.24.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "6b86639c01e2be18b9e08a99d5aa46e09747cade936cc703d9d30bfe8d61fa1c", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem 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"src/backend/nodes/tidbitmap.c", "sha256": "6b86639c01e2be18b9e08a99d5aa46e09747cade936cc703d9d30bfe8d61fa1c", "archive_sha256": "a7fa7ed3d558172355f51406097a7bd4f6b473be80f311ef7cda96bf383d8897"}, {"url": "https://pg.center/docs/14/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 14.24 \u00b7 using-explain", "sha256": "7f5ab59cb21a035ada45ea3426c5d1cca3f781273483677f73fdd76753555206", "language": "en", "original_url": "/docs/14/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.07..229.20 rows=101 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/14/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 14.24 \u00b7 using-explain", "sha256": "7f5ab59cb21a035ada45ea3426c5d1cca3f781273483677f73fdd76753555206"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 14.24 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..229.43 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/14/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 14.24 \u00b7 using-explain", "sha256": "7f5ab59cb21a035ada45ea3426c5d1cca3f781273483677f73fdd76753555206"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 14.24 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002"], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/14/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/14/facts/3/label": "Output", "/versions/14/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Examples from this manual build", "/versions/14/sections/4/title": "Executor implementation notes", "/versions/14/sections/5/title": "EXPLAIN identity in core source", "/versions/14/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/versions/14/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/14/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/14/sections/4/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/14/sections/4/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/14/sections/4/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/14/sections/4/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/14/sections/4/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/14/tables/0/columns/0/label": "Text-format label", "/versions/14/tables/0/columns/1/label": "Structured node identity", "/versions/14/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 14.24 manual; it was not executed for this collection.", "/versions/14/sections/3/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/14/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 14.24 manual; it was not executed for this collection.", "/versions/14/sections/3/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "6efb503db5424f075c651c5defaef07ca62c5b8327fdd05ee66220a4595a1ac5"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"value": "ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "56086022a2c2ceeed972a69beb7594243f1e2b09be987893500d37a9527587d1", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, {"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "4abf4a8e67412488d65490b4e292043351122be09f03af97150b384dc7ee11bb", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem 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"src/backend/nodes/tidbitmap.c", "sha256": "4abf4a8e67412488d65490b4e292043351122be09f03af97150b384dc7ee11bb", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, {"url": "https://pg.center/docs/15/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 15.19 \u00b7 using-explain", "sha256": "d1f509457c647da453d2575c772d91022a0f115dd84f9a3b20f5ff25a243648f", "language": "en", "original_url": "/docs/15/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.07..229.20 rows=101 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/15/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 15.19 \u00b7 using-explain", "sha256": "d1f509457c647da453d2575c772d91022a0f115dd84f9a3b20f5ff25a243648f"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 15.19 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..229.43 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/15/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 15.19 \u00b7 using-explain", "sha256": "d1f509457c647da453d2575c772d91022a0f115dd84f9a3b20f5ff25a243648f"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 15.19 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002"], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/15/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/15/facts/3/label": "Output", "/versions/15/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Examples from this manual build", "/versions/15/sections/4/title": "Executor implementation notes", "/versions/15/sections/5/title": "EXPLAIN identity in core source", "/versions/15/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/versions/15/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/15/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/15/sections/4/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/15/sections/4/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/15/sections/4/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/15/sections/4/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/15/sections/4/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/15/tables/0/columns/0/label": "Text-format label", "/versions/15/tables/0/columns/1/label": "Structured node identity", "/versions/15/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 15.19 manual; it was not executed for this collection.", "/versions/15/sections/3/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/15/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 15.19 manual; it was not executed for this collection.", "/versions/15/sections/3/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "904cfd3ac97e05ea59e832efea91fbc99ab0861413af48f256a2427ed94faa4b"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"value": "ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "8d736785d991187397f0ceb21eb8b59bbab598d0a5dde1c36976239a34306a48", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, {"url": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "d0a2549a532f65299aea5599ee1bedffe47101a07d0de21bec07068547ae237e", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem 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"src/backend/nodes/tidbitmap.c", "sha256": "d0a2549a532f65299aea5599ee1bedffe47101a07d0de21bec07068547ae237e", "archive_sha256": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, {"url": "https://pg.center/docs/16/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 16.15 \u00b7 using-explain", "sha256": "bd8b86e5281cf0e52ad6e0e4bb8b6ff6510dac61982b44f0c1dd07d54012db3c", "language": "en", "original_url": "/docs/16/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.07..229.20 rows=101 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/16/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 16.15 \u00b7 using-explain", "sha256": "bd8b86e5281cf0e52ad6e0e4bb8b6ff6510dac61982b44f0c1dd07d54012db3c"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 16.15 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..229.43 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0)\n         Index Cond: (unique1 < 100)", "source": {"url": "/docs/16/using-explain.html#USING-EXPLAIN-BASICS", "path": "using-explain.html", "label": "PostgreSQL 16.15 \u00b7 using-explain", "sha256": "bd8b86e5281cf0e52ad6e0e4bb8b6ff6510dac61982b44f0c1dd07d54012db3c"}, "paragraphs": ["\u793a\u4f8b\u6458\u81ea PostgreSQL 16.15 \u624b\u518c\uff1b\u672c\u767e\u79d1\u672a\u5b9e\u9645\u6267\u884c\u6b64\u793a\u4f8b\u3002", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002"], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/16/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/16/facts/3/label": "Output", "/versions/16/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Examples from this manual build", "/versions/16/sections/4/title": "Executor implementation notes", "/versions/16/sections/5/title": "EXPLAIN identity in core source", "/versions/16/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/versions/16/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/16/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/16/sections/4/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/16/sections/4/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/16/sections/4/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/16/sections/4/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/16/sections/4/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/16/tables/0/columns/0/label": "Text-format label", "/versions/16/tables/0/columns/1/label": "Structured node identity", "/versions/16/sections/3/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 16.15 manual; it was not executed for this collection.", "/versions/16/sections/3/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/16/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 16.15 manual; it was not executed for this collection.", "/versions/16/sections/3/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "dfeb9f514c52a172e97f2e974c75afa6752c81653427821f590e931e57bddd0a"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"value": "ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "f5c09276ecc3c8d7956a511944e4c4f832ff9180292dd7b398f7a109113a7276", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, {"url": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "10f9875b7384fddcd0750b41f7357933769a840c57a7bc0e29eecd4cdc5b8f4c", "archive_sha256": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem 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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\uff1anone extracted from this node implementation."]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.06..224.98 rows=100 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..225.20 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\u3002"], "localization": {"status": "complete", "sources": [], "language": "zh", "original_text": {"/versions/17/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/17/facts/3/label": "Output", "/versions/17/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/versions/17/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/17/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/17/sections/4/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/17/sections/4/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/17/sections/4/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/17/sections/4/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/17/sections/4/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/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": "Now, let's make the condition more restrictive:", "/versions/17/sections/3/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 17.11 manual; it was not executed for this collection.", "/versions/17/sections/3/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "955ebd9aaecbe80075ddf20302eaf0ae2ff0fb23b61eb5acb22f5a79cce93f28"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": "T_BitmapIndexScan", "strategies": [], "text_names": ["Bitmap Index Scan"], "initializer": "ExecInitBitmapIndexScan", "partial_modes": [], "memory_mechanism": "bitmap-lossification", "parallel_callbacks": []}, "comparison_hash": "b81114c9864c11cc43d2183d9c32e01632186cff8cced0f6ff218f56f56485c0", "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/nodeBitmapIndexscan.c"}, "parallel_callbacks": []}, "18": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_BitmapIndexScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Bitmap Index Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15"}, {"label": "\u8f93\u51fa", "value": "\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\uff0c\u4e0d\u662f\u5143\u7ec4\u6d41"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "7eed6439851a24333252fcce6e7c71856e8da9bdaee78597401b11afdbb093c0", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "e2453b7155d55db8c3a59bc929362f01d3f9692b0a483e5aa81a7b6c50db6102", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}], "mechanism": "bitmap-lossification", "description": "\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\u3002", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Bitmap Index Scan", "identity": "Bitmap Index 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_bitmapscan/?v=18", "label": "enable_bitmapscan"}, {"url": "/wiki/guc/work_mem/?v=18", "label": "work_mem"}, {"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": 1450, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1450", "sha256": "34c86d6070224a0e981efef51f79101d6d505e5874f1684ace183034bab14bb4", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "line": 229, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:229", "sha256": "f8a06a3f539077249b20664b2812433db6d7bd12b2c0ca633525db43d06f112a", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "7eed6439851a24333252fcce6e7c71856e8da9bdaee78597401b11afdbb093c0", "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://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": "e2453b7155d55db8c3a59bc929362f01d3f9692b0a483e5aa81a7b6c50db6102", "archive_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, {"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"}, {"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"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\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\uff1aExecBitmapIndexScanEstimate, ExecBitmapIndexScanInitializeDSM, ExecBitmapIndexScanInitializeWorker, ExecBitmapIndexScanRetrieveInstrumentation."]}, {"title": "\u540c\u7248\u672c\u624b\u518c\u8bf4\u660e", "paragraphs": ["Index Scan \u8282\u70b9\uff08\u4ee5\u53ca Bitmap Index Scan \u548c Index-Only Scan \u8282\u70b9\uff09\u4f1a\u663e\u793a\u4e00\u884c \u201c Index Searches \u201d \uff0c\u7528\u4e8e\u62a5\u544a\u8de8 \u6240\u6709 \u8282\u70b9\u6267\u884c/ loops \u7684\u603b\u641c\u7d22\u6b21\u6570\uff1a", "\u8fd9\u91cc\u7684 Bitmap Index Scan \u8282\u70b9\u9700\u8981\u5206\u522b\u6267\u884c 4 \u6b21\u7d22\u5f15\u641c\u7d22\u3002\u5bf9\u4e8e\u8c13\u8bcd IN \u7ed3\u6784\u4e2d\u7684\u6bcf\u4e2a\u6574\u6570\u503c\uff0c\u626b\u63cf\u90fd\u9700\u8981\u4ece tenk1_thous_tenthous \u7d22\u5f15\u7684\u6839\u9875\u5f00\u59cb\u641c\u7d22\u4e00\u6b21\u3002\u4e0d\u8fc7\uff0c\u7d22\u5f15\u641c\u7d22\u6b21\u6570\u5f80\u5f80\u4e0d\u4f1a\u4e0e\u67e5\u8be2\u8c13\u8bcd\u5b58\u5728\u5982\u6b64\u7b80\u5355\u7684\u5bf9\u5e94\u5173\u7cfb\uff1a"]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.06..224.98 rows=100 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..225.20 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\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[8]/p[8]"]}], "language": "zh", "original_text": {"/versions/18/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/18/facts/3/label": "Output", "/versions/18/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Same-version manual discussion", "/versions/18/sections/4/title": "Examples from this manual build", "/versions/18/sections/5/title": "Executor implementation notes", "/versions/18/sections/6/title": "EXPLAIN identity in core source", "/versions/18/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: ExecBitmapIndexScanEstimate, ExecBitmapIndexScanInitializeDSM, ExecBitmapIndexScanInitializeWorker, ExecBitmapIndexScanRetrieveInstrumentation.", "/versions/18/sections/3/paragraphs/0": "Index Scan nodes (as well as Bitmap Index Scan and Index-Only Scan nodes) show an \u201c Index Searches \u201d line that reports the total number of searches across all node executions/ loops :", "/versions/18/sections/3/paragraphs/1": "Here we see a Bitmap Index Scan node that needed 4 separate index searches. The scan had to search the index from the tenk1_thous_tenthous index root page once per integer value from the predicate's IN construct. However, the number of index searches often won't have such a simple correspondence to the query predicate:", "/versions/18/sections/5/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/18/sections/5/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/18/sections/5/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/18/sections/5/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/18/sections/5/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/18/tables/0/columns/0/label": "Text-format label", "/versions/18/tables/0/columns/1/label": "Structured node identity", "/versions/18/sections/4/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 18.6 manual; it was not executed for this collection.", "/versions/18/sections/4/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/18/sections/4/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 18.6 manual; it was not executed for this collection.", "/versions/18/sections/4/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "855e33ae188369035d13ceabcd53070c74f3db8662a05b8592e8e6c5378af6c2"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": "T_BitmapIndexScan", "strategies": [], "text_names": ["Bitmap Index Scan"], "initializer": "ExecInitBitmapIndexScan", "partial_modes": [], "memory_mechanism": "bitmap-lossification", "parallel_callbacks": ["ExecBitmapIndexScanEstimate", "ExecBitmapIndexScanInitializeDSM", "ExecBitmapIndexScanInitializeWorker", "ExecBitmapIndexScanRetrieveInstrumentation"]}, "comparison_hash": "08e8d1afde24882a70dccba204ec21bdcea148fa12f7f53d14a221b80af1cc37", "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/nodeBitmapIndexscan.c"}, "parallel_callbacks": ["ExecBitmapIndexScanEstimate", "ExecBitmapIndexScanInitializeDSM", "ExecBitmapIndexScanInitializeWorker", "ExecBitmapIndexScanRetrieveInstrumentation"]}, "19": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_BitmapIndexScan"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN 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"52f111fbd213e2200146319d01a9dcc2ea90001617d2a28edc52f7954c2dd70b", "language": "en", "original_url": "/docs/19/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\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\uff1aExecBitmapIndexScanEstimate, ExecBitmapIndexScanInitializeDSM, ExecBitmapIndexScanInitializeWorker, ExecBitmapIndexScanRetrieveInstrumentation."]}, {"title": "\u540c\u7248\u672c\u624b\u518c\u8bf4\u660e", "paragraphs": ["Index Scan \u8282\u70b9\uff08\u4ee5\u53ca Bitmap Index Scan \u548c Index-Only Scan \u8282\u70b9\uff09\u4f1a\u663e\u793a\u4e00\u884c \u201c Index Searches \u201d \uff0c\u7528\u4e8e\u62a5\u544a\u8de8 \u6240\u6709 \u8282\u70b9\u6267\u884c/ loops \u7684\u603b\u641c\u7d22\u6b21\u6570\uff1a", "\u8fd9\u91cc\u7684 Bitmap Index Scan \u8282\u70b9\u9700\u8981\u5206\u522b\u6267\u884c 4 \u6b21\u7d22\u5f15\u641c\u7d22\u3002\u5bf9\u4e8e\u8c13\u8bcd IN \u7ed3\u6784\u4e2d\u7684\u6bcf\u4e2a\u6574\u6570\u503c\uff0c\u626b\u63cf\u90fd\u9700\u8981\u4ece tenk1_thous_tenthous \u7d22\u5f15\u7684\u6839\u9875\u5f00\u59cb\u641c\u7d22\u4e00\u6b21\u3002\u4e0d\u8fc7\uff0c\u7d22\u5f15\u641c\u7d22\u6b21\u6570\u5f80\u5f80\u4e0d\u4f1a\u4e0e\u67e5\u8be2\u8c13\u8bcd\u5b58\u5728\u5982\u6b64\u7b80\u5355\u7684\u5bf9\u5e94\u5173\u7cfb\uff1a"]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.06..224.98 rows=100 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..225.20 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\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[8]/p[11]"]}], "language": "zh", "original_text": {"/versions/19/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/19/facts/3/label": "Output", "/versions/19/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Same-version manual discussion", "/versions/19/sections/4/title": "Examples from this manual build", "/versions/19/sections/5/title": "Executor implementation notes", "/versions/19/sections/6/title": "EXPLAIN identity in core source", "/versions/19/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: ExecBitmapIndexScanEstimate, ExecBitmapIndexScanInitializeDSM, ExecBitmapIndexScanInitializeWorker, ExecBitmapIndexScanRetrieveInstrumentation.", "/versions/19/sections/3/paragraphs/0": "Index Scan nodes (as well as Bitmap Index Scan and Index-Only Scan nodes) show an \u201c Index Searches \u201d line that reports the total number of searches across all node executions/ loops :", "/versions/19/sections/3/paragraphs/1": "Here we see a Bitmap Index Scan node that needed 4 separate index searches. The scan had to search the index from the tenk1_thous_tenthous index root page once per integer value from the predicate's IN construct. However, the number of index searches often won't have such a simple correspondence to the query predicate:", "/versions/19/sections/5/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/19/sections/5/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/19/sections/5/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/19/sections/5/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/19/sections/5/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/19/tables/0/columns/0/label": "Text-format label", "/versions/19/tables/0/columns/1/label": "Structured node identity", "/versions/19/sections/4/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 19beta4 manual; it was not executed for this collection.", "/versions/19/sections/4/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/19/sections/4/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 19beta4 manual; it was not executed for this collection.", "/versions/19/sections/4/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "21ae4e31f3b73711e508524900a2e86caa3c2e5c6ca088e4f04707cc676965de"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Bitmap Index Scan"}, {"label": "\u8f93\u5165", "value": "\u7d22\u5f15"}, {"label": "\u8f93\u51fa", "value": "\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\uff0c\u4e0d\u662f\u5143\u7ec4\u6d41"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitBitmapIndexScan"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "bitmap-lossification"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "1beaa9f9767d3d4fd4670f8a1e9b78fed47485973ff842b5b9e620e94edd14d1", "archive_sha256": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}, {"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "path": "src/backend/nodes/tidbitmap.c", "label": "src/backend/nodes/tidbitmap.c", "sha256": 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"4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}, {"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "line": 229, "path": "src/backend/executor/execProcnode.c", "label": "src/backend/executor/execProcnode.c:229", "sha256": "5e39b2037bed672da55104229ecc32da5abde44c26bcad01479edcfa044d09ed", "archive_sha256": "4d3346909b201ac1648232cf290462a7070c119326f56196f1f0253ed80fae41"}, {"url": "https://ftp.postgresql.org/pub/snapshot/dev/postgresql-snapshot.tar.bz2", "path": "src/backend/executor/nodeBitmapIndexscan.c", "label": "src/backend/executor/nodeBitmapIndexscan.c", "sha256": "1beaa9f9767d3d4fd4670f8a1e9b78fed47485973ff842b5b9e620e94edd14d1", "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": 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"99cfea3035876ea63f88b75ba8c964b51a32a70606544e09f769c0b60a234b31", "language": "en", "original_url": "/docs/devel/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\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\uff1aExecBitmapIndexScanEstimate, ExecBitmapIndexScanInitializeDSM, ExecBitmapIndexScanInitializeWorker, ExecBitmapIndexScanRetrieveInstrumentation."]}, {"title": "\u540c\u7248\u672c\u624b\u518c\u8bf4\u660e", "paragraphs": ["Index Scan \u8282\u70b9\uff08\u4ee5\u53ca Bitmap Index Scan \u548c Index-Only Scan \u8282\u70b9\uff09\u4f1a\u663e\u793a\u4e00\u884c \u201c Index Searches \u201d \uff0c\u7528\u4e8e\u62a5\u544a\u8de8 \u6240\u6709 \u8282\u70b9\u6267\u884c/ loops \u7684\u603b\u641c\u7d22\u6b21\u6570\uff1a", "\u8fd9\u91cc\u7684 Bitmap Index Scan \u8282\u70b9\u9700\u8981\u5206\u522b\u6267\u884c 4 \u6b21\u7d22\u5f15\u641c\u7d22\u3002\u5bf9\u4e8e\u8c13\u8bcd IN \u7ed3\u6784\u4e2d\u7684\u6bcf\u4e2a\u6574\u6570\u503c\uff0c\u626b\u63cf\u90fd\u9700\u8981\u4ece tenk1_thous_tenthous \u7d22\u5f15\u7684\u6839\u9875\u5f00\u59cb\u641c\u7d22\u4e00\u6b21\u3002\u4e0d\u8fc7\uff0c\u7d22\u5f15\u641c\u7d22\u6b21\u6570\u5f80\u5f80\u4e0d\u4f1a\u4e0e\u67e5\u8be2\u8c13\u8bcd\u5b58\u5728\u5982\u6b64\u7b80\u5355\u7684\u5bf9\u5e94\u5173\u7cfb\uff1a"]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.06..224.98 rows=100 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..225.20 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\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[8]/p[11]"]}], "language": "zh", "original_text": {"/summary": "Scans an index and produces a bitmap of matching tuple locations.", "/category": "Bitmap", "/versions/20/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/20/facts/3/label": "Output", "/versions/20/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Same-version manual discussion", "/versions/20/sections/4/title": "Examples from this manual build", "/versions/20/sections/5/title": "Executor implementation notes", "/versions/20/sections/6/title": "EXPLAIN identity in core source", "/versions/20/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: ExecBitmapIndexScanEstimate, ExecBitmapIndexScanInitializeDSM, ExecBitmapIndexScanInitializeWorker, ExecBitmapIndexScanRetrieveInstrumentation.", "/versions/20/sections/3/paragraphs/0": "Index Scan nodes (as well as Bitmap Index Scan and Index-Only Scan nodes) show an \u201c Index Searches \u201d line that reports the total number of searches across all node executions/ loops :", "/versions/20/sections/3/paragraphs/1": "Here we see a Bitmap Index Scan node that needed 4 separate index searches. The scan had to search the index from the tenk1_thous_tenthous index root page once per integer value from the predicate's IN construct. However, the number of index searches often won't have such a simple correspondence to the query predicate:", "/versions/20/sections/5/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/20/sections/5/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/20/sections/5/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/20/sections/5/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/20/sections/5/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/20/tables/0/columns/0/label": "Text-format label", "/versions/20/tables/0/columns/1/label": "Structured node identity", "/versions/20/sections/4/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 20devel manual; it was not executed for this collection.", "/versions/20/sections/4/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/20/sections/4/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 20devel manual; it was not executed for this collection.", "/versions/20/sections/4/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "9b66deb9fdb2ba8c7882b816ca18e0684718f34313f852305f46c46dcf49ecb7"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": 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"60040c30180093418a0affe56dd27dff9df2504b705b38039589e458bf5c31ed", "language": "en", "original_url": "/docs/18/using-explain.html#USING-EXPLAIN-BASICS"}], "node_tag": "T_BitmapIndexScan", "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\uff1aBitmap Index 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": ["\u6b64\u8282\u70b9\u6309\u57fa\u4e8e work_mem \u7684\u9884\u7b97\u5206\u914d\u5143\u7ec4\u4f4d\u7f6e\u4f4d\u56fe\u3002\u4f4d\u56fe\u53ef\u4ee5\u4fdd\u7559\u9875\u7ea7\u6709\u635f\u6761\u76ee\uff0c\u800c\u4e0d\u8bb0\u5f55\u6bcf\u4e2a\u5143\u7ec4\u4f4d\u7f6e\uff0c\u56e0\u6b64\u4ecd\u53ef\u80fd\u9700\u8981\u5806\u91cd\u68c0\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\uff1aExecBitmapIndexScanEstimate, ExecBitmapIndexScanInitializeDSM, ExecBitmapIndexScanInitializeWorker, ExecBitmapIndexScanRetrieveInstrumentation."]}, {"title": "\u540c\u7248\u672c\u624b\u518c\u8bf4\u660e", "paragraphs": ["Index Scan \u8282\u70b9\uff08\u4ee5\u53ca Bitmap Index Scan \u548c Index-Only Scan \u8282\u70b9\uff09\u4f1a\u663e\u793a\u4e00\u884c \u201c Index Searches \u201d \uff0c\u7528\u4e8e\u62a5\u544a\u8de8 \u6240\u6709 \u8282\u70b9\u6267\u884c/ loops \u7684\u603b\u641c\u7d22\u6b21\u6570\uff1a", "\u8fd9\u91cc\u7684 Bitmap Index Scan \u8282\u70b9\u9700\u8981\u5206\u522b\u6267\u884c 4 \u6b21\u7d22\u5f15\u641c\u7d22\u3002\u5bf9\u4e8e\u8c13\u8bcd IN \u7ed3\u6784\u4e2d\u7684\u6bcf\u4e2a\u6574\u6570\u503c\uff0c\u626b\u63cf\u90fd\u9700\u8981\u4ece tenk1_thous_tenthous \u7d22\u5f15\u7684\u6839\u9875\u5f00\u59cb\u641c\u7d22\u4e00\u6b21\u3002\u4e0d\u8fc7\uff0c\u7d22\u5f15\u641c\u7d22\u6b21\u6570\u5f80\u5f80\u4e0d\u4f1a\u4e0e\u67e5\u8be2\u8c13\u8bcd\u5b58\u5728\u5982\u6b64\u7b80\u5355\u7684\u5bf9\u5e94\u5173\u7cfb\uff1a"]}, {"title": "\u672c\u7248\u624b\u518c\u4e2d\u7684\u793a\u4f8b", "blocks": [{"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100;\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.06..224.98 rows=100 width=244)\n   Recheck Cond: (unique1 < 100)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u8fdb\u4e00\u6b65\u6536\u7d27\u6761\u4ef6\uff1a"]}, {"code": "EXPLAIN SELECT * FROM tenk1 WHERE unique1 < 100 AND stringu1 = 'xxx';\n\n                                  QUERY PLAN\n------------------------------------------------------------------------------\n Bitmap Heap Scan on tenk1  (cost=5.04..225.20 rows=1 width=244)\n   Recheck Cond: (unique1 < 100)\n   Filter: (stringu1 = 'xxx'::name)\n   ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=100 width=0)\n         Index Cond: (unique1 < 100)", "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", "\u73b0\u5728\u5411 WHERE \u5b50\u53e5\u518d\u6dfb\u52a0\u4e00\u4e2a\u6761\u4ef6\uff1a"]}]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeBitmapIndexscan.c\uff1a\u652f\u6301\u5173\u7cfb\u4f4d\u56fe\u7d22\u5f15\u626b\u63cf\u7684\u4f8b\u7a0b\u3002", "\u5982\u679c\u6709\u8fd0\u884c\u65f6\u952e\u4e14\u5c1a\u672a\u8bbe\u7f6e\uff0c\u73b0\u5728\u5c31\u8bbe\u7f6e\u3002\u6570\u7ec4\u952e\u4e5f\u89c6\u4e3a\u8fd0\u884c\u65f6\u952e\uff1b\u6ce8\u610f\uff0c\u5982\u679c ExecReScan \u8fd4\u56de\u540e biss_RuntimeKeysReady \u4ecd\u4e3a false\uff0c\u5219\u5b58\u5728\u7a7a\u6570\u7ec4\u952e\uff0c\u6b64\u65f6\u4e0d\u5e94\u6267\u884c\u4efb\u4f55\u64cd\u4f5c\u3002", "\u51c6\u5907\u7ed3\u679c\u4f4d\u56fe\u3002\u901a\u5e38\u521b\u5efa\u65b0\u4f4d\u56fe\u8fd4\u56de\uff1b\u4f46\u7236\u8282\u70b9\u53ef\u4ee5\u9884\u5148\u5728 node->biss_result \u4e2d\u5b58\u5165\u4f4d\u56fe\uff0c\u6b64\u65f6\u76f4\u63a5\u5c06\u5143\u7ec4 ID \u6309\u4f4d OR \u5408\u5e76\u5230\u73b0\u6709\u4f4d\u56fe\uff0c\u7701\u53bb\u663e\u5f0f UNION \u6b65\u9aa4\u3002", "\u91cd\u65b0\u8ba1\u7b97\u4f9d\u8d56\u8fd0\u884c\u65f6\u4fe1\u606f\u7684\u626b\u63cf\u952e\u503c\uff0c\u7136\u540e\u91cd\u65b0\u626b\u63cf\u88ab\u7d22\u5f15\u7684\u5173\u7cfb\u3002", "\u91cd\u7f6e\u8fd0\u884c\u65f6\u952e\u4e0a\u4e0b\u6587\uff0c\u907f\u514d\u6bcf\u6b21\u626b\u63cf\u5916\u4fa7\u5143\u7ec4\u65f6\u6cc4\u6f0f\u5185\u5b58\u3002\u8fd9\u91cc\u5047\u5b9a\u6bcf\u6b21\u8c03\u7528\u90fd\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u8fd0\u884c\u65f6\u952e\u3002"]}, {"code": "case T_BitmapIndexScan:\n\t\t\tpname = sname = \"Bitmap Index Scan\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u626b\u63cf\u7d22\u5f15\uff0c\u5e76\u751f\u6210\u5339\u914d\u5143\u7ec4\u4f4d\u7f6e\u7684\u4f4d\u56fe\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[8]/p[8]"]}], "language": "zh", "original_text": {"/versions/18/description/0": "Scans an index and produces a bitmap of matching tuple locations.", "/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", "/versions/18/facts/3/label": "Output", "/versions/18/facts/3/value": "Tuple-location bitmap, not a tuple stream", "/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": "Same-version manual discussion", "/versions/18/sections/4/title": "Examples from this manual build", "/versions/18/sections/5/title": "Executor implementation notes", "/versions/18/sections/6/title": "EXPLAIN identity in core source", "/versions/18/memory/description": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: Bitmap Index 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": "The node allocates a tuple-location bitmap using a work_mem-derived budget. A bitmap can retain page-level lossy entries instead of every tuple location; heap rechecks then remain necessary.", "/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: ExecBitmapIndexScanEstimate, ExecBitmapIndexScanInitializeDSM, ExecBitmapIndexScanInitializeWorker, ExecBitmapIndexScanRetrieveInstrumentation.", "/versions/18/sections/3/paragraphs/0": "Index Scan nodes (as well as Bitmap Index Scan and Index-Only Scan nodes) show an \u201c Index Searches \u201d line that reports the total number of searches across all node executions/ loops :", "/versions/18/sections/3/paragraphs/1": "Here we see a Bitmap Index Scan node that needed 4 separate index searches. The scan had to search the index from the tenk1_thous_tenthous index root page once per integer value from the predicate's IN construct. However, the number of index searches often won't have such a simple correspondence to the query predicate:", "/versions/18/sections/5/paragraphs/0": "nodeBitmapIndexscan.c Routines to support bitmapped index scans of relations", "/versions/18/sections/5/paragraphs/1": "If we have runtime keys and they've not already been set up, do it now. Array keys are also treated as runtime keys; note that if ExecReScan returns with biss_RuntimeKeysReady still false, then there is an empty array key so we should do nothing.", "/versions/18/sections/5/paragraphs/2": "Prepare the result bitmap. Normally we just create a new one to pass back; however, our parent node is allowed to store a pre-made one into node->biss_result, in which case we just OR our tuple IDs into the existing bitmap. (This saves needing explicit UNION steps.)", "/versions/18/sections/5/paragraphs/3": "Recalculates the values of any scan keys whose value depends on information known at runtime, then rescans the indexed relation.", "/versions/18/sections/5/paragraphs/4": "Reset the runtime-key context so we don't leak memory as each outer tuple is scanned. Note this assumes that we will recalculate *all* runtime keys on each call.", "/versions/18/tables/0/columns/0/label": "Text-format label", "/versions/18/tables/0/columns/1/label": "Structured node identity", "/versions/18/sections/4/blocks/0/paragraphs/0": "Example copied from the PostgreSQL 18.6 manual; it was not executed for this collection.", "/versions/18/sections/4/blocks/0/paragraphs/1": "Now, let's make the condition more restrictive:", "/versions/18/sections/4/blocks/1/paragraphs/0": "Example copied from the PostgreSQL 18.6 manual; it was not executed for this collection.", "/versions/18/sections/4/blocks/1/paragraphs/1": "Now let's add another condition to the WHERE clause:"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "855e33ae188369035d13ceabcd53070c74f3db8662a05b8592e8e6c5378af6c2"}, "evidence_kind": "source and documentation", "explain_names": ["Bitmap Index Scan"], "partial_modes": [], "comparison_data": {"node_tag": "T_BitmapIndexScan", "strategies": [], "text_names": ["Bitmap Index Scan"], "initializer": "ExecInitBitmapIndexScan", "partial_modes": [], "memory_mechanism": "bitmap-lossification", "parallel_callbacks": ["ExecBitmapIndexScanEstimate", "ExecBitmapIndexScanInitializeDSM", "ExecBitmapIndexScanInitializeWorker", "ExecBitmapIndexScanRetrieveInstrumentation"]}, "comparison_hash": "08e8d1afde24882a70dccba204ec21bdcea148fa12f7f53d14a221b80af1cc37", "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/nodeBitmapIndexscan.c"}, "parallel_callbacks": ["ExecBitmapIndexScanEstimate", "ExecBitmapIndexScanInitializeDSM", "ExecBitmapIndexScanInitializeWorker", "ExecBitmapIndexScanRetrieveInstrumentation"]}, "comparison": {"left": "17", "right": "18", "status": "changed", "diff": "--- PostgreSQL 17\n+++ PostgreSQL 18\n@@ -2,7 +2,12 @@\n   \"initializer\": \"ExecInitBitmapIndexScan\",\n   \"memory_mechanism\": \"bitmap-lossification\",\n   \"node_tag\": \"T_BitmapIndexScan\",\n-  \"parallel_callbacks\": [],\n+  \"parallel_callbacks\": [\n+    \"ExecBitmapIndexScanEstimate\",\n+    \"ExecBitmapIndexScanInitializeDSM\",\n+    \"ExecBitmapIndexScanInitializeWorker\",\n+    \"ExecBitmapIndexScanRetrieveInstrumentation\"\n+  ],\n   \"partial_modes\": [],\n   \"strategies\": [],\n   \"text_names\": ["}}