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Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.", "Text names recorded by this source: Sample Scan.", "Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node."]}, {"title": "Memory and temporary storage", "paragraphs": ["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."]}, {"title": "Parallel execution and instrumentation", "paragraphs": ["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.", "Callbacks in this build: none extracted from this node implementation."]}, {"title": "Executor implementation notes", "paragraphs": ["nodeSamplescan.c Support routines for sample scans of relations (table sampling).", "SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual", "No need to recheck for SampleScan, since like SeqScan we don't pass any checkable keys to heap_beginscan.", "Scans the relation using the sampling method and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.", "If we don't have a REPEATABLE clause, select a random seed. We want to do this just once, since the seed shouldn't change over rescans."]}, {"code": "case T_SampleScan:\n\t\t\tpname = sname = \"Sample Scan\";\n\t\t\tbreak;", "title": "EXPLAIN identity in core source"}], "strategies": [], "description": ["Reads a relation using the selected table-sampling method."], "evidence_kind": "source and documentation", "explain_names": ["Sample Scan"], "partial_modes": [], "comparison_data": {"node_tag": "T_SampleScan", "strategies": [], "text_names": ["Sample Scan"], "initializer": "ExecInitSampleScan", "partial_modes": [], "memory_mechanism": "unclassified", "parallel_callbacks": []}, "comparison_hash": "353ba2b42b3d419de2b0fd5f49ddf5d460404fbad27fe1fded7536333a1bedeb", "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/nodeSamplescan.c"}, "parallel_callbacks": []}, "comparison": {"left": "17", "right": "18", "status": "unchanged", "diff": ""}}