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["nodeGroup.c\uff1a\u5904\u7406 Group \u8282\u70b9\uff08\u7528\u4e8e\u5e26 GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\uff09\u7684\u4f8b\u7a0b\u3002", "\u8bf4\u660e\uff1aGroup \u8282\u70b9\u7528\u4e8e\u5904\u7406\u5305\u542b GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\u3002\u5b83\u7684\u5916\u4fa7\u8ba1\u5212\u5fc5\u987b\u6309\u5206\u7ec4\u5217\u6307\u5b9a\u7684\u987a\u5e8f\u8f93\u51fa\u5143\u7ec4\uff0c\u5373\u540c\u7ec4\u5143\u7ec4\u5fc5\u987b\u8fde\u7eed\u3002\u8fd9\u6837\uff0c\u53ea\u9700\u6bd4\u8f83\u76f8\u90bb\u5143\u7ec4\u5373\u53ef\u786e\u5b9a\u5206\u7ec4\u8fb9\u754c\u3002", "ScanTupleSlot \u4fdd\u5b58\u6bcf\u4e2a\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7ec4\u7684\u526f\u672c\u3002", "\u6b64\u5904\u65e0\u9700\u8c03\u7528 ResetExprContext\uff0c\u56e0\u4e3a ExecQualAndReset() \u4f1a\u4e3a\u6bcf\u4e2a\u8f93\u5165\u5143\u7ec4\u91cd\u7f6e\u4e00\u6b21\u9010\u5143\u7ec4\u5185\u5b58\u4e0a\u4e0b\u6587\u3002", 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Inspect the same-build implementation and its expressions or provider.", "/versions/12/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/12/sections/0/paragraphs/1": "Text names recorded by this source: Group.", "/versions/12/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/12/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/12/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/12/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/12/sections/3/paragraphs/0": "PostgreSQL supports parallel aggregation by aggregating in two stages. First, each process participating in the parallel portion of the query performs an aggregation step, producing a partial result for each group of which that process is aware. This is reflected in the plan as a Partial Aggregate node. Second, the partial results are transferred to the leader via Gather or Gather Merge . Finally, the leader re-aggregates the results across all workers in order to produce the final result. This is reflected in the plan as a Finalize Aggregate node.", "/versions/12/sections/4/paragraphs/0": "nodeGroup.c Routines to handle group nodes (used for queries with GROUP BY clause).", "/versions/12/sections/4/paragraphs/1": "DESCRIPTION The Group node is designed for handling queries with a GROUP BY clause. Its outer plan must deliver tuples that are sorted in the order specified by the grouping columns (ie. tuples from the same group are consecutive). That way, we just have to compare adjacent tuples to locate group boundaries.", "/versions/12/sections/4/paragraphs/2": "The ScanTupleSlot holds the (copied) first tuple of each group.", "/versions/12/sections/4/paragraphs/3": "We need not call ResetExprContext here because ExecQualAndReset() will reset the per-tuple memory context once per input tuple.", "/versions/12/sections/4/paragraphs/4": "If first time through, acquire first input tuple and determine whether to return it or not.", "/versions/12/tables/0/columns/0/label": "Text-format label", "/versions/12/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "f9c9670ef29fffce291b73f57fbd479c845b19f75972561af8204a5527bcf86f"}, "evidence_kind": "source and documentation", "explain_names": ["Group"], "partial_modes": [], "comparison_data": {"node_tag": "T_Group", "strategies": [], "text_names": ["Group"], "initializer": "ExecInitGroup", "partial_modes": 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["nodeGroup.c\uff1a\u5904\u7406 Group \u8282\u70b9\uff08\u7528\u4e8e\u5e26 GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\uff09\u7684\u4f8b\u7a0b\u3002", "\u8bf4\u660e\uff1aGroup \u8282\u70b9\u7528\u4e8e\u5904\u7406\u5305\u542b GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\u3002\u5b83\u7684\u5916\u4fa7\u8ba1\u5212\u5fc5\u987b\u6309\u5206\u7ec4\u5217\u6307\u5b9a\u7684\u987a\u5e8f\u8f93\u51fa\u5143\u7ec4\uff0c\u5373\u540c\u7ec4\u5143\u7ec4\u5fc5\u987b\u8fde\u7eed\u3002\u8fd9\u6837\uff0c\u53ea\u9700\u6bd4\u8f83\u76f8\u90bb\u5143\u7ec4\u5373\u53ef\u786e\u5b9a\u5206\u7ec4\u8fb9\u754c\u3002", "ScanTupleSlot \u4fdd\u5b58\u6bcf\u4e2a\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7ec4\u7684\u526f\u672c\u3002", "\u6b64\u5904\u65e0\u9700\u8c03\u7528 ResetExprContext\uff0c\u56e0\u4e3a ExecQualAndReset() \u4f1a\u4e3a\u6bcf\u4e2a\u8f93\u5165\u5143\u7ec4\u91cd\u7f6e\u4e00\u6b21\u9010\u5143\u7ec4\u5185\u5b58\u4e0a\u4e0b\u6587\u3002", "\u9996\u6b21\u6267\u884c\u65f6\uff0c\u83b7\u53d6\u7b2c\u4e00\u4e2a\u8f93\u5165\u5143\u7ec4\uff0c\u5e76\u5224\u65ad\u662f\u5426\u5e94\u8fd4\u56de\u5b83\u3002"]}, {"code": "case T_Group:\n\t\t\tpname = sname = \"Group\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u6309\u5206\u7ec4\u5217\u5bf9\u6709\u5e8f\u8f93\u5165\u6d41\u8fdb\u884c\u5206\u7ec4\u3002"], "localization": {"status": "complete", "sources": [{"url": "/docs/13/parallel-plans.html", "method": "same-major semantic node", "sha256": "bbbbbd9cc27db6811c388e9c4951a9641c48871942bc709cec203e4271518c50", "language": "zh", "matched_nodes": ["#PARALLEL-PLANS/div[5]/p[1]"]}], "language": "zh", "original_text": {"/versions/13/description/0": "Groups an ordered input stream by its grouping columns.", "/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": "One ordered child plan", "/versions/13/facts/3/label": "Output", "/versions/13/facts/3/value": "One tuple per group", "/versions/13/facts/4/label": "Executor initializer", "/versions/13/facts/5/label": "Memory mechanism", "/versions/13/tables/0/title": "EXPLAIN labels in this source build", "/versions/13/related/1/label": "Using EXPLAIN", "/versions/13/related/2/label": "Parallel plans", "/versions/13/sections/0/title": "EXPLAIN names and attributes", "/versions/13/sections/1/title": "Memory and temporary storage", "/versions/13/sections/2/title": "Parallel execution and instrumentation", "/versions/13/sections/3/title": "Same-version manual discussion", "/versions/13/sections/4/title": "Executor implementation notes", "/versions/13/sections/5/title": "EXPLAIN identity in core source", "/versions/13/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/13/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/13/sections/0/paragraphs/1": "Text names recorded by this source: Group.", "/versions/13/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/13/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/13/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/13/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/13/sections/3/paragraphs/0": "PostgreSQL supports parallel aggregation by aggregating in two stages. First, each process participating in the parallel portion of the query performs an aggregation step, producing a partial result for each group of which that process is aware. This is reflected in the plan as a Partial Aggregate node. Second, the partial results are transferred to the leader via Gather or Gather Merge . Finally, the leader re-aggregates the results across all workers in order to produce the final result. This is reflected in the plan as a Finalize Aggregate node.", "/versions/13/sections/4/paragraphs/0": "nodeGroup.c Routines to handle group nodes (used for queries with GROUP BY clause).", "/versions/13/sections/4/paragraphs/1": "DESCRIPTION The Group node is designed for handling queries with a GROUP BY clause. Its outer plan must deliver tuples that are sorted in the order specified by the grouping columns (ie. tuples from the same group are consecutive). That way, we just have to compare adjacent tuples to locate group boundaries.", "/versions/13/sections/4/paragraphs/2": "The ScanTupleSlot holds the (copied) first tuple of each group.", "/versions/13/sections/4/paragraphs/3": "We need not call ResetExprContext here because ExecQualAndReset() will reset the per-tuple memory context once per input tuple.", "/versions/13/sections/4/paragraphs/4": "If first time through, acquire first input tuple and determine whether to return it or not.", "/versions/13/tables/0/columns/0/label": "Text-format label", "/versions/13/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "51dc705bc280538a9a156fe4c294bf1efd4437f18b467ab75a82274679361906"}, "evidence_kind": "source and documentation", "explain_names": ["Group"], "partial_modes": [], "comparison_data": {"node_tag": "T_Group", "strategies": [], "text_names": ["Group"], "initializer": "ExecInitGroup", "partial_modes": 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"path": "parallel-plans.html", "label": "PostgreSQL 14.24 \u00b7 parallel-plans", "sha256": "71fc3525781b74150364925e123cd8598fdebe0e05326706f2bc2e1ffa0b88a4", "language": "en", "original_url": "/docs/14/parallel-plans.html#PARALLEL-AGGREGATION"}], "node_tag": "T_Group", "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\uff1aGroup.", "\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": 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\u901a\u8fc7\u5206\u4e24\u4e2a\u9636\u6bb5\u8fdb\u884c\u805a\u5408\u6765\u652f\u6301\u5e76\u884c\u805a\u5408\u3002\u9996\u5148\uff0c\u6bcf\u4e2a\u53c2\u4e0e\u67e5\u8be2\u5e76\u884c\u90e8\u5206\u7684\u8fdb\u7a0b\u6267\u884c\u4e00\u4e2a\u805a\u5408\u6b65\u9aa4\uff0c\u4e3a\u8be5\u8fdb\u7a0b\u6240\u89c1\u5230\u7684\u6bcf\u4e2a\u5206\u7ec4\u4ea7\u751f\u4e00\u4e2a\u90e8\u5206\u7ed3\u679c\u3002\u8fd9\u5728\u8ba1\u5212\u4e2d\u4f53\u73b0\u4e3a\u4e00\u4e2a Partial Aggregate \u8282\u70b9\u3002\u7136\u540e\uff0c\u90e8\u5206\u7ed3\u679c\u901a\u8fc7 Gather \u6216 Gather Merge \u4f20\u9001\u7ed9\u9886\u5bfc\u8005\u3002\u6700\u540e\uff0c\u9886\u5bfc\u8005\u4f1a\u628a\u6765\u81ea\u6240\u6709\u5de5\u4f5c\u8fdb\u7a0b\u7684\u7ed3\u679c\u518d\u6b21\u805a\u5408\uff0c\u4ee5\u4ea7\u751f\u6700\u7ec8\u7ed3\u679c\u3002\u8fd9\u5728\u8ba1\u5212\u4e2d\u4f53\u73b0\u4e3a\u4e00\u4e2a Finalize Aggregate \u8282\u70b9\u3002"]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeGroup.c\uff1a\u5904\u7406 Group \u8282\u70b9\uff08\u7528\u4e8e\u5e26 GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\uff09\u7684\u4f8b\u7a0b\u3002", "\u8bf4\u660e\uff1aGroup \u8282\u70b9\u7528\u4e8e\u5904\u7406\u5305\u542b GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\u3002\u5b83\u7684\u5916\u4fa7\u8ba1\u5212\u5fc5\u987b\u6309\u5206\u7ec4\u5217\u6307\u5b9a\u7684\u987a\u5e8f\u8f93\u51fa\u5143\u7ec4\uff0c\u5373\u540c\u7ec4\u5143\u7ec4\u5fc5\u987b\u8fde\u7eed\u3002\u8fd9\u6837\uff0c\u53ea\u9700\u6bd4\u8f83\u76f8\u90bb\u5143\u7ec4\u5373\u53ef\u786e\u5b9a\u5206\u7ec4\u8fb9\u754c\u3002", "ScanTupleSlot \u4fdd\u5b58\u6bcf\u4e2a\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7ec4\u7684\u526f\u672c\u3002", "\u6b64\u5904\u65e0\u9700\u8c03\u7528 ResetExprContext\uff0c\u56e0\u4e3a ExecQualAndReset() \u4f1a\u4e3a\u6bcf\u4e2a\u8f93\u5165\u5143\u7ec4\u91cd\u7f6e\u4e00\u6b21\u9010\u5143\u7ec4\u5185\u5b58\u4e0a\u4e0b\u6587\u3002", "\u9996\u6b21\u6267\u884c\u65f6\uff0c\u83b7\u53d6\u7b2c\u4e00\u4e2a\u8f93\u5165\u5143\u7ec4\uff0c\u5e76\u5224\u65ad\u662f\u5426\u5e94\u8fd4\u56de\u5b83\u3002"]}, {"code": "case T_Group:\n\t\t\tpname = sname = \"Group\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u6309\u5206\u7ec4\u5217\u5bf9\u6709\u5e8f\u8f93\u5165\u6d41\u8fdb\u884c\u5206\u7ec4\u3002"], "localization": {"status": "complete", "sources": [{"url": "/docs/14/parallel-plans.html", "method": "same-major semantic node", "sha256": "27ba0fab61ef7b5aa518b18597a7cd30f9560e5cf2b383016d31e59518892f88", "language": "zh", "matched_nodes": ["#PARALLEL-PLANS/div[5]/p[1]"]}], "language": "zh", "original_text": {"/versions/14/description/0": "Groups an ordered input stream by its grouping columns.", "/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": "One ordered child plan", "/versions/14/facts/3/label": "Output", "/versions/14/facts/3/value": "One tuple per group", "/versions/14/facts/4/label": "Executor initializer", "/versions/14/facts/5/label": "Memory mechanism", "/versions/14/tables/0/title": "EXPLAIN labels in this source build", "/versions/14/related/1/label": "Using EXPLAIN", "/versions/14/related/2/label": "Parallel plans", "/versions/14/sections/0/title": "EXPLAIN names and attributes", "/versions/14/sections/1/title": "Memory and temporary storage", "/versions/14/sections/2/title": "Parallel execution and instrumentation", "/versions/14/sections/3/title": "Same-version manual discussion", "/versions/14/sections/4/title": "Executor implementation notes", "/versions/14/sections/5/title": "EXPLAIN identity in core source", "/versions/14/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/14/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/14/sections/0/paragraphs/1": "Text names recorded by this source: Group.", "/versions/14/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/14/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/14/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/14/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/14/sections/3/paragraphs/0": "PostgreSQL supports parallel aggregation by aggregating in two stages. First, each process participating in the parallel portion of the query performs an aggregation step, producing a partial result for each group of which that process is aware. This is reflected in the plan as a Partial Aggregate node. Second, the partial results are transferred to the leader via Gather or Gather Merge . Finally, the leader re-aggregates the results across all workers in order to produce the final result. This is reflected in the plan as a Finalize Aggregate node.", "/versions/14/sections/4/paragraphs/0": "nodeGroup.c Routines to handle group nodes (used for queries with GROUP BY clause).", "/versions/14/sections/4/paragraphs/1": "DESCRIPTION The Group node is designed for handling queries with a GROUP BY clause. Its outer plan must deliver tuples that are sorted in the order specified by the grouping columns (ie. tuples from the same group are consecutive). That way, we just have to compare adjacent tuples to locate group boundaries.", "/versions/14/sections/4/paragraphs/2": "The ScanTupleSlot holds the (copied) first tuple of each group.", "/versions/14/sections/4/paragraphs/3": "We need not call ResetExprContext here because ExecQualAndReset() will reset the per-tuple memory context once per input tuple.", "/versions/14/sections/4/paragraphs/4": "If first time through, acquire first input tuple and determine whether to return it or not.", "/versions/14/tables/0/columns/0/label": "Text-format label", "/versions/14/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "fd299c8e54ce4b432428a8c255ff17fc583bbf50d603d41ffd39b0ef5d0a864b"}, "evidence_kind": "source and documentation", "explain_names": ["Group"], "partial_modes": [], "comparison_data": {"node_tag": "T_Group", "strategies": [], "text_names": ["Group"], "initializer": "ExecInitGroup", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "c75b880801aecfa8f510650c6bb3c2e0aa820810550fefe9c62d04727c0c0048", "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/nodeGroup.c"}, "parallel_callbacks": []}, "15": {"facts": [{"label": "\u6838\u5fc3\u8282\u70b9\u6807\u7b7e", "value": "T_Group"}, {"label": "\u7ed3\u6784\u5316 EXPLAIN \u8282\u70b9\u7c7b\u578b", "value": "Group"}, {"label": "\u8f93\u5165", "value": "\u4e00\u4e2a\u6709\u5e8f\u5b50\u8ba1\u5212"}, {"label": "\u8f93\u51fa", "value": "\u6bcf\u7ec4\u4e00\u4e2a\u5143\u7ec4"}, {"label": "\u6267\u884c\u5668\u521d\u59cb\u5316\u51fd\u6570", "value": "ExecInitGroup"}, {"label": "\u5185\u5b58\u673a\u5236", "value": "unclassified"}], "memory": {"evidence": [{"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "path": "src/backend/executor/nodeGroup.c", "label": "src/backend/executor/nodeGroup.c", "sha256": "fe2b6f000c8b63acad78c9e5b673a7918d057e414f4c734d5d4be7f4fd87e96c", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}], "mechanism": "unclassified", "description": "\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002", "source_notes": []}, "tables": [{"key": "explain-labels", "rows": [{"label": "Group", "identity": "Group"}], "title": "\u672c\u6784\u5efa\u4e2d\u7684 EXPLAIN \u6807\u7b7e", "columns": [{"key": "label", "label": "\u6587\u672c\u683c\u5f0f\u6807\u7b7e"}, {"key": "identity", "label": "\u7ed3\u6784\u5316\u8282\u70b9\u6807\u8bc6"}]}], "related": [{"url": "/wiki/sql/explain/?v=15", "label": "EXPLAIN"}, {"url": "/docs/15/using-explain.html", "label": "\u4f7f\u7528 EXPLAIN"}, {"url": "/docs/15/parallel-plans.html", "label": "\u5e76\u884c\u8ba1\u5212"}], "release": {"ref": "PostgreSQL 15.19 source archive", "label": "15.19", "major": "15", "channel": "stable", "revision": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89", "source_url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "source_snapshot_utc": ""}, "sources": [{"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "line": 1321, "path": "src/backend/commands/explain.c", "label": "src/backend/commands/explain.c:1321", "sha256": "bb3b442d0f1b098aa8707335250102f027a596cd94117308bd16d1d36b258f5c", "archive_sha256": "e1a64a87a46b825b88c082e4518161a47aab53c45694964f8ba1df28f7859f89"}, {"url": "https://ftp.postgresql.org/pub/source/v15.19/postgresql-15.19.tar.bz2", "line": 335, "path": 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"path": "parallel-plans.html", "label": "PostgreSQL 15.19 \u00b7 parallel-plans", "sha256": "ec9345488a15cdc05d3e0b0849763e2bf0b864ad17de786c5f023db5dab1ea96", "language": "en", "original_url": "/docs/15/parallel-plans.html#PARALLEL-AGGREGATION"}], "node_tag": "T_Group", "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\uff1aGroup.", "\u5e76\u884c\u611f\u77e5\u4e0e\u5e76\u884c\u5b89\u5168\u662f\u4e0d\u540c\u7684\u8ba1\u5212\u5c5e\u6027\u3002\u5728\u5e76\u884c\u5de5\u4f5c\u8fdb\u7a0b\u5185\u8fd0\u884c\u7684\u8282\u70b9\u4e0d\u4e00\u5b9a\u662f\u5e76\u884c\u611f\u77e5\u8282\u70b9\u3002"]}, {"title": "\u5185\u5b58\u4e0e\u4e34\u65f6\u5b58\u50a8", "paragraphs": ["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"title": "\u5e76\u884c\u6267\u884c\u4e0e\u8fd0\u884c\u4fe1\u606f\u91c7\u96c6", "paragraphs": ["\u4ee5\u4e0b\u6e90\u7801\u56de\u8c03\u53ef\u4ee5\u534f\u8c03\u6267\u884c\u6216\u6536\u96c6\u5de5\u4f5c\u8fdb\u7a0b\u7684\u6d4b\u91cf\u6570\u636e\u3002\u56de\u8c03\u5b58\u5728\u4e0d\u4ee3\u8868\u8be5\u8282\u70b9\u666e\u904d\u652f\u6301\u5171\u4eab\u5e76\u884c\u626b\u63cf\u6216\u5171\u4eab\u72b6\u6001\u3002", "\u6b64\u6784\u5efa\u7684\u56de\u8c03\uff1anone extracted from this node implementation."]}, {"title": "\u540c\u7248\u672c\u624b\u518c\u8bf4\u660e", "paragraphs": ["PostgreSQL \u901a\u8fc7\u5206\u4e24\u4e2a\u9636\u6bb5\u8fdb\u884c\u805a\u5408\u6765\u652f\u6301\u5e76\u884c\u805a\u5408\u3002\u9996\u5148\uff0c\u6bcf\u4e2a\u53c2\u4e0e\u67e5\u8be2\u5e76\u884c\u90e8\u5206\u7684\u8fdb\u7a0b\u6267\u884c\u4e00\u4e2a\u805a\u5408\u6b65\u9aa4\uff0c\u4e3a\u8be5\u8fdb\u7a0b\u6240\u89c1\u5230\u7684\u6bcf\u4e2a\u5206\u7ec4\u4ea7\u751f\u4e00\u4e2a\u90e8\u5206\u7ed3\u679c\u3002\u8fd9\u5728\u8ba1\u5212\u4e2d\u4f53\u73b0\u4e3a\u4e00\u4e2a Partial Aggregate \u8282\u70b9\u3002\u7136\u540e\uff0c\u90e8\u5206\u7ed3\u679c\u901a\u8fc7 Gather \u6216 Gather Merge \u4f20\u9001\u7ed9\u9886\u5bfc\u8005\u3002\u6700\u540e\uff0c\u9886\u5bfc\u8005\u4f1a\u628a\u6765\u81ea\u6240\u6709\u5de5\u4f5c\u8fdb\u7a0b\u7684\u7ed3\u679c\u518d\u6b21\u805a\u5408\uff0c\u4ee5\u4ea7\u751f\u6700\u7ec8\u7ed3\u679c\u3002\u8fd9\u5728\u8ba1\u5212\u4e2d\u4f53\u73b0\u4e3a\u4e00\u4e2a Finalize Aggregate \u8282\u70b9\u3002"]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeGroup.c\uff1a\u5904\u7406 Group \u8282\u70b9\uff08\u7528\u4e8e\u5e26 GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\uff09\u7684\u4f8b\u7a0b\u3002", "\u8bf4\u660e\uff1aGroup \u8282\u70b9\u7528\u4e8e\u5904\u7406\u5305\u542b GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\u3002\u5b83\u7684\u5916\u4fa7\u8ba1\u5212\u5fc5\u987b\u6309\u5206\u7ec4\u5217\u6307\u5b9a\u7684\u987a\u5e8f\u8f93\u51fa\u5143\u7ec4\uff0c\u5373\u540c\u7ec4\u5143\u7ec4\u5fc5\u987b\u8fde\u7eed\u3002\u8fd9\u6837\uff0c\u53ea\u9700\u6bd4\u8f83\u76f8\u90bb\u5143\u7ec4\u5373\u53ef\u786e\u5b9a\u5206\u7ec4\u8fb9\u754c\u3002", "ScanTupleSlot \u4fdd\u5b58\u6bcf\u4e2a\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7ec4\u7684\u526f\u672c\u3002", "\u6b64\u5904\u65e0\u9700\u8c03\u7528 ResetExprContext\uff0c\u56e0\u4e3a ExecQualAndReset() \u4f1a\u4e3a\u6bcf\u4e2a\u8f93\u5165\u5143\u7ec4\u91cd\u7f6e\u4e00\u6b21\u9010\u5143\u7ec4\u5185\u5b58\u4e0a\u4e0b\u6587\u3002", 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"/versions/15/facts/2/value": "One ordered child plan", "/versions/15/facts/3/label": "Output", "/versions/15/facts/3/value": "One tuple per group", "/versions/15/facts/4/label": "Executor initializer", "/versions/15/facts/5/label": "Memory mechanism", "/versions/15/tables/0/title": "EXPLAIN labels in this source build", "/versions/15/related/1/label": "Using EXPLAIN", "/versions/15/related/2/label": "Parallel plans", "/versions/15/sections/0/title": "EXPLAIN names and attributes", "/versions/15/sections/1/title": "Memory and temporary storage", "/versions/15/sections/2/title": "Parallel execution and instrumentation", "/versions/15/sections/3/title": "Same-version manual discussion", "/versions/15/sections/4/title": "Executor implementation notes", "/versions/15/sections/5/title": "EXPLAIN identity in core source", "/versions/15/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. 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["nodeGroup.c\uff1a\u5904\u7406 Group \u8282\u70b9\uff08\u7528\u4e8e\u5e26 GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\uff09\u7684\u4f8b\u7a0b\u3002", "\u8bf4\u660e\uff1aGroup \u8282\u70b9\u7528\u4e8e\u5904\u7406\u5305\u542b GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\u3002\u5b83\u7684\u5916\u4fa7\u8ba1\u5212\u5fc5\u987b\u6309\u5206\u7ec4\u5217\u6307\u5b9a\u7684\u987a\u5e8f\u8f93\u51fa\u5143\u7ec4\uff0c\u5373\u540c\u7ec4\u5143\u7ec4\u5fc5\u987b\u8fde\u7eed\u3002\u8fd9\u6837\uff0c\u53ea\u9700\u6bd4\u8f83\u76f8\u90bb\u5143\u7ec4\u5373\u53ef\u786e\u5b9a\u5206\u7ec4\u8fb9\u754c\u3002", "ScanTupleSlot \u4fdd\u5b58\u6bcf\u4e2a\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7ec4\u7684\u526f\u672c\u3002", "\u6b64\u5904\u65e0\u9700\u8c03\u7528 ResetExprContext\uff0c\u56e0\u4e3a ExecQualAndReset() \u4f1a\u4e3a\u6bcf\u4e2a\u8f93\u5165\u5143\u7ec4\u91cd\u7f6e\u4e00\u6b21\u9010\u5143\u7ec4\u5185\u5b58\u4e0a\u4e0b\u6587\u3002", 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Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/16/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/16/sections/3/paragraphs/0": "PostgreSQL supports parallel aggregation by aggregating in two stages. First, each process participating in the parallel portion of the query performs an aggregation step, producing a partial result for each group of which that process is aware. This is reflected in the plan as a Partial Aggregate node. Second, the partial results are transferred to the leader via Gather or Gather Merge . Finally, the leader re-aggregates the results across all workers in order to produce the final result. This is reflected in the plan as a Finalize Aggregate node.", "/versions/16/sections/4/paragraphs/0": "nodeGroup.c Routines to handle group nodes (used for queries with GROUP BY clause).", "/versions/16/sections/4/paragraphs/1": "DESCRIPTION The Group node is designed for handling queries with a GROUP BY clause. Its outer plan must deliver tuples that are sorted in the order specified by the grouping columns (ie. tuples from the same group are consecutive). 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Inspect the same-build implementation and its expressions or provider.", "/versions/17/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/17/sections/0/paragraphs/1": "Text names recorded by this source: Group.", "/versions/17/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/17/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/17/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/17/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/17/sections/3/paragraphs/0": "PostgreSQL supports parallel aggregation by aggregating in two stages. First, each process participating in the parallel portion of the query performs an aggregation step, producing a partial result for each group of which that process is aware. This is reflected in the plan as a Partial Aggregate node. Second, the partial results are transferred to the leader via Gather or Gather Merge . Finally, the leader re-aggregates the results across all workers in order to produce the final result. 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build", "/versions/19/related/1/label": "Using EXPLAIN", "/versions/19/related/2/label": "Parallel plans", "/versions/19/sections/0/title": "EXPLAIN names and attributes", "/versions/19/sections/1/title": "Memory and temporary storage", "/versions/19/sections/2/title": "Parallel execution and instrumentation", "/versions/19/sections/3/title": "Same-version manual discussion", "/versions/19/sections/4/title": "Executor implementation notes", "/versions/19/sections/5/title": "EXPLAIN identity in core source", "/versions/19/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/19/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/19/sections/0/paragraphs/1": "Text names recorded by this source: Group.", "/versions/19/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/19/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/19/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/19/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/19/sections/3/paragraphs/0": "PostgreSQL supports parallel aggregation by aggregating in two stages. First, each process participating in the parallel portion of the query performs an aggregation step, producing a partial result for each group of which that process is aware. This is reflected in the plan as a Partial Aggregate node. Second, the partial results are transferred to the leader via Gather or Gather Merge . Finally, the leader re-aggregates the results across all workers in order to produce the final result. 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That way, we just have to compare adjacent tuples to locate group boundaries.", "/versions/19/sections/4/paragraphs/2": "The ScanTupleSlot holds the (copied) first tuple of each group.", "/versions/19/sections/4/paragraphs/3": "We need not call ResetExprContext here because ExecQualAndReset() will reset the per-tuple memory context once per input tuple.", "/versions/19/sections/4/paragraphs/4": "If first time through, acquire first input tuple and determine whether to return it or not.", "/versions/19/tables/0/columns/0/label": "Text-format label", "/versions/19/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "e83d6457fd3a64bdad231739cb759cc779d329da8614e74fba4e8905f6553642"}, "evidence_kind": "source and documentation", "explain_names": ["Group"], "partial_modes": [], "comparison_data": {"node_tag": "T_Group", "strategies": [], "text_names": ["Group"], "initializer": "ExecInitGroup", "partial_modes": 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"strategies": [], "description": ["\u6309\u5206\u7ec4\u5217\u5bf9\u6709\u5e8f\u8f93\u5165\u6d41\u8fdb\u884c\u5206\u7ec4\u3002"], "localization": {"status": "complete", "sources": [{"url": "/docs/devel/parallel-plans.html", "method": "same-major semantic node", "sha256": "322333100879d0971d33685d4924d0c6b79bc429a74a35f9cca60c247e02b545", "language": "zh", "matched_nodes": ["#PARALLEL-PLANS/div[5]/p[1]"]}], "language": "zh", "original_text": {"/summary": "Groups an ordered input stream by its grouping columns.", "/category": "Aggregation", "/versions/20/description/0": "Groups an ordered input stream by its grouping columns.", "/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": "One ordered child plan", "/versions/20/facts/3/label": "Output", "/versions/20/facts/3/value": "One tuple per group", "/versions/20/facts/4/label": "Executor initializer", "/versions/20/facts/5/label": "Memory mechanism", "/versions/20/tables/0/title": "EXPLAIN labels in this source build", "/versions/20/related/1/label": "Using EXPLAIN", "/versions/20/related/2/label": "Parallel plans", "/versions/20/sections/0/title": "EXPLAIN names and attributes", "/versions/20/sections/1/title": "Memory and temporary storage", "/versions/20/sections/2/title": "Parallel execution and instrumentation", "/versions/20/sections/3/title": "Same-version manual discussion", "/versions/20/sections/4/title": "Executor implementation notes", "/versions/20/sections/5/title": "EXPLAIN identity in core source", "/versions/20/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/20/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/20/sections/0/paragraphs/1": "Text names recorded by this source: Group.", "/versions/20/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/20/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/20/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/20/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/20/sections/3/paragraphs/0": "PostgreSQL supports parallel aggregation by aggregating in two stages. First, each process participating in the parallel portion of the query performs an aggregation step, producing a partial result for each group of which that process is aware. This is reflected in the plan as a Partial Aggregate node. Second, the partial results are transferred to the leader via Gather or Gather Merge . Finally, the leader re-aggregates the results across all workers in order to produce the final result. This is reflected in the plan as a Finalize Aggregate node.", "/versions/20/sections/4/paragraphs/0": "nodeGroup.c Routines to handle group nodes (used for queries with GROUP BY clause).", "/versions/20/sections/4/paragraphs/1": "DESCRIPTION The Group node is designed for handling queries with a GROUP BY clause. Its outer plan must deliver tuples that are sorted in the order specified by the grouping columns (ie. tuples from the same group are consecutive). That way, we just have to compare adjacent tuples to locate group boundaries.", "/versions/20/sections/4/paragraphs/2": "The ScanTupleSlot holds the (copied) first tuple of each group.", "/versions/20/sections/4/paragraphs/3": "We need not call ResetExprContext here because ExecQualAndReset() will reset the per-tuple memory context once per input tuple.", "/versions/20/sections/4/paragraphs/4": "If first time through, acquire first input tuple and determine whether to return it or not.", "/versions/20/tables/0/columns/0/label": "Text-format label", "/versions/20/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "b63be608d20010e3fb24de52528ec389050c45d6860faa21bb3190d4cacf76c8"}, "evidence_kind": "source and documentation", "explain_names": ["Group"], "partial_modes": [], "comparison_data": {"node_tag": "T_Group", "strategies": [], "text_names": ["Group"], "initializer": "ExecInitGroup", "partial_modes": 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["\u672c\u6b21\u62bd\u53d6\u4e0d\u4e3a\u6b64\u8282\u70b9\u8bbe\u5b9a\u7edf\u4e00\u7684\u5185\u5b58\u4e0a\u9650\u6216\u843d\u76d8\u7b56\u7565\u3002\u8bf7\u67e5\u770b\u540c\u4e00\u6784\u5efa\u7684\u5b9e\u73b0\u3001\u76f8\u5173\u8868\u8fbe\u5f0f\u6216\u63d0\u4f9b\u65b9\u3002"]}, {"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": "\u540c\u7248\u672c\u624b\u518c\u8bf4\u660e", "paragraphs": ["PostgreSQL \u901a\u8fc7\u5206\u4e24\u4e2a\u9636\u6bb5\u8fdb\u884c\u805a\u5408\u6765\u652f\u6301\u5e76\u884c\u805a\u5408\u3002\u9996\u5148\uff0c\u6bcf\u4e2a\u53c2\u4e0e\u67e5\u8be2\u5e76\u884c\u90e8\u5206\u7684\u8fdb\u7a0b\u6267\u884c\u4e00\u4e2a\u805a\u5408\u6b65\u9aa4\uff0c\u4e3a\u8be5\u8fdb\u7a0b\u6240\u89c1\u5230\u7684\u6bcf\u4e2a\u5206\u7ec4\u4ea7\u751f\u4e00\u4e2a\u90e8\u5206\u7ed3\u679c\u3002\u8fd9\u5728\u8ba1\u5212\u4e2d\u4f53\u73b0\u4e3a\u4e00\u4e2a Partial Aggregate \u8282\u70b9\u3002\u7136\u540e\uff0c\u90e8\u5206\u7ed3\u679c\u901a\u8fc7 Gather \u6216 Gather Merge \u4f20\u9001\u7ed9\u9886\u5bfc\u8005\u3002\u6700\u540e\uff0c\u9886\u5bfc\u8005\u4f1a\u628a\u6765\u81ea\u6240\u6709\u5de5\u4f5c\u8fdb\u7a0b\u7684\u7ed3\u679c\u518d\u6b21\u805a\u5408\uff0c\u4ee5\u4ea7\u751f\u6700\u7ec8\u7ed3\u679c\u3002\u8fd9\u5728\u8ba1\u5212\u4e2d\u4f53\u73b0\u4e3a\u4e00\u4e2a Finalize Aggregate \u8282\u70b9\u3002"]}, {"title": "\u6267\u884c\u5668\u5b9e\u73b0\u8bf4\u660e", "paragraphs": ["nodeGroup.c\uff1a\u5904\u7406 Group \u8282\u70b9\uff08\u7528\u4e8e\u5e26 GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\uff09\u7684\u4f8b\u7a0b\u3002", "\u8bf4\u660e\uff1aGroup \u8282\u70b9\u7528\u4e8e\u5904\u7406\u5305\u542b GROUP BY \u5b50\u53e5\u7684\u67e5\u8be2\u3002\u5b83\u7684\u5916\u4fa7\u8ba1\u5212\u5fc5\u987b\u6309\u5206\u7ec4\u5217\u6307\u5b9a\u7684\u987a\u5e8f\u8f93\u51fa\u5143\u7ec4\uff0c\u5373\u540c\u7ec4\u5143\u7ec4\u5fc5\u987b\u8fde\u7eed\u3002\u8fd9\u6837\uff0c\u53ea\u9700\u6bd4\u8f83\u76f8\u90bb\u5143\u7ec4\u5373\u53ef\u786e\u5b9a\u5206\u7ec4\u8fb9\u754c\u3002", "ScanTupleSlot \u4fdd\u5b58\u6bcf\u4e2a\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7ec4\u7684\u526f\u672c\u3002", "\u6b64\u5904\u65e0\u9700\u8c03\u7528 ResetExprContext\uff0c\u56e0\u4e3a ExecQualAndReset() \u4f1a\u4e3a\u6bcf\u4e2a\u8f93\u5165\u5143\u7ec4\u91cd\u7f6e\u4e00\u6b21\u9010\u5143\u7ec4\u5185\u5b58\u4e0a\u4e0b\u6587\u3002", "\u9996\u6b21\u6267\u884c\u65f6\uff0c\u83b7\u53d6\u7b2c\u4e00\u4e2a\u8f93\u5165\u5143\u7ec4\uff0c\u5e76\u5224\u65ad\u662f\u5426\u5e94\u8fd4\u56de\u5b83\u3002"]}, {"code": "case T_Group:\n\t\t\tpname = sname = \"Group\";\n\t\t\tbreak;", "title": "\u6838\u5fc3\u6e90\u7801\u4e2d\u7684 EXPLAIN \u6807\u8bc6"}], "strategies": [], "description": ["\u6309\u5206\u7ec4\u5217\u5bf9\u6709\u5e8f\u8f93\u5165\u6d41\u8fdb\u884c\u5206\u7ec4\u3002"], "localization": {"status": "complete", "sources": [{"url": "/docs/18/parallel-plans.html", "method": "same-major semantic node", "sha256": "7fa104623c0b4cd22acf0929e40518fbed8fe368af3e3b124cf693bd7ab69f0c", "language": "zh", "matched_nodes": ["#PARALLEL-PLANS/div[5]/p[1]"]}], "language": "zh", "original_text": {"/versions/18/description/0": "Groups an ordered input stream by its grouping columns.", "/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": "One ordered child plan", "/versions/18/facts/3/label": "Output", "/versions/18/facts/3/value": "One tuple per group", "/versions/18/facts/4/label": "Executor initializer", "/versions/18/facts/5/label": "Memory mechanism", "/versions/18/tables/0/title": "EXPLAIN labels in this source build", "/versions/18/related/1/label": "Using EXPLAIN", "/versions/18/related/2/label": "Parallel plans", "/versions/18/sections/0/title": "EXPLAIN names and attributes", "/versions/18/sections/1/title": "Memory and temporary storage", "/versions/18/sections/2/title": "Parallel execution and instrumentation", "/versions/18/sections/3/title": "Same-version manual discussion", "/versions/18/sections/4/title": "Executor implementation notes", "/versions/18/sections/5/title": "EXPLAIN identity in core source", "/versions/18/memory/description": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/18/sections/0/paragraphs/0": "Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "/versions/18/sections/0/paragraphs/1": "Text names recorded by this source: Group.", "/versions/18/sections/0/paragraphs/2": "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.", "/versions/18/sections/1/paragraphs/0": "This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.", "/versions/18/sections/2/paragraphs/0": "The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.", "/versions/18/sections/2/paragraphs/1": "Callbacks in this build: none extracted from this node implementation.", "/versions/18/sections/3/paragraphs/0": "PostgreSQL supports parallel aggregation by aggregating in two stages. First, each process participating in the parallel portion of the query performs an aggregation step, producing a partial result for each group of which that process is aware. This is reflected in the plan as a Partial Aggregate node. Second, the partial results are transferred to the leader via Gather or Gather Merge . Finally, the leader re-aggregates the results across all workers in order to produce the final result. This is reflected in the plan as a Finalize Aggregate node.", "/versions/18/sections/4/paragraphs/0": "nodeGroup.c Routines to handle group nodes (used for queries with GROUP BY clause).", "/versions/18/sections/4/paragraphs/1": "DESCRIPTION The Group node is designed for handling queries with a GROUP BY clause. Its outer plan must deliver tuples that are sorted in the order specified by the grouping columns (ie. tuples from the same group are consecutive). That way, we just have to compare adjacent tuples to locate group boundaries.", "/versions/18/sections/4/paragraphs/2": "The ScanTupleSlot holds the (copied) first tuple of each group.", "/versions/18/sections/4/paragraphs/3": "We need not call ResetExprContext here because ExecQualAndReset() will reset the per-tuple memory context once per input tuple.", "/versions/18/sections/4/paragraphs/4": "If first time through, acquire first input tuple and determine whether to return it or not.", "/versions/18/tables/0/columns/0/label": "Text-format label", "/versions/18/tables/0/columns/1/label": "Structured node identity"}, "fallback_fields": [], "source_language": "en", "original_snapshot_sha256": "56ac798dcd46d2de90819a36fd7ce8ab41db34afa3fb54b0f3acf8526141cadc"}, "evidence_kind": "source and documentation", "explain_names": ["Group"], "partial_modes": [], "comparison_data": {"node_tag": "T_Group", "strategies": [], "text_names": ["Group"], "initializer": "ExecInitGroup", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "c75b880801aecfa8f510650c6bb3c2e0aa820810550fefe9c62d04727c0c0048", "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/nodeGroup.c"}, "parallel_callbacks": []}, "comparison": {"left": "17", "right": "18", "status": "unchanged", "diff": ""}}