Table Function Scan

Description

Scans the rows produced by a table function such as XMLTABLE.

Core node tag

T_TableFuncScan

Structured EXPLAIN Node Type

Table Function Scan

Inputs

A table-function expression

Output

Table-function result tuples

Executor initializer

ExecInitTableFuncScan

Memory mechanism

tuplestore

EXPLAIN names and attributes

Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.

Text names recorded by this source: Table Function Scan.

Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.

Memory and temporary storage

This node creates a tuplestore with work_mem. The tuplestore can move stored tuples to temporary files; this does not make work_mem a cap on every allocation made by the node.

Parallel execution and instrumentation

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.

Executor implementation notes

nodeTableFuncscan.c Support routines for scanning RangeTableFunc (XMLTABLE like functions).

If first time through, read all tuples from function and put them in a tuplestore. Subsequent calls just fetch tuples from tuplestore.

TableFuncRecheck -- access method routine to recheck a tuple in EvalPlanQual

Scans the function sequentially and returns the next qualifying tuple. We call the ExecScan() routine and pass it the appropriate access method functions.

Each call to fetch a new set of rows - of which there may be very many if XMLTABLE or JSON_TABLE is being used in a lateral join - will allocate a possibly substantial amount of memory, so we cannot use the per-query context here. perTableCxt now serves the same function as "argcontext" does in FunctionScan - a place to store per-one-call (i.e. one result table) lifetime data (as opposed to per-query or per-result-tuple).

EXPLAIN identity in core source

case T_TableFuncScan:
			pname = sname = "Table Function Scan";
			break;

Related entries

• EXPLAIN
• Using EXPLAIN
• Parallel plans
• work_mem

Documentation and source

• src/backend/commands/explain.c:1468
• src/backend/executor/execProcnode.c:259
• src/backend/executor/nodeTableFuncscan.c
• src/include/nodes/plannodes.h
• src/backend/utils/sort/tuplestore.c

Compare versions

PostgreSQL 17 → 18: unchanged.

Compares recorded interfaces and attributes. Source fingerprints and build metadata are excluded; an absent sample is not proof of the introduction or removal release.

Related entries

• Bitmap Heap ScanBitmapHeapScan
• CTE ScanCteScan
• Function ScanFunctionScan
• Index Only ScanIndexOnlyScan
• Index ScanIndexScan
• Named Tuplestore ScanNamedTuplestoreScan
• Sample ScanSampleScan
• Seq ScanSeqScan
• Subquery ScanSubqueryScan
• Tid Range ScanTidRangeScan
• Tid ScanTidScan
• Values ScanValuesScan