Function ExecMakeTableFunctionResult

src/backend/executor/execSRF.c:100–439

* ExecMakeTableFunctionResult * * Evaluate a table function, producing a materialized result in a Tuplestore * object. * * This is used by nodeFunctionscan.c. */

 * This is used by nodeFunctionscan.c.
 */
Tuplestorestate *
ExecMakeTableFunctionResult(SetExprState *setexpr,
							ExprContext *econtext,
							MemoryContext argContext,
							TupleDesc expectedDesc,
							bool randomAccess,
							uint64 operatorMemKB)
{
	Tuplestorestate *tupstore = NULL;
	TupleDesc	tupdesc = NULL;
	Oid			funcrettype;
	bool		returnsTuple;
	bool		returnsSet = false;
	FunctionCallInfo fcinfo;
	PgStat_FunctionCallUsage fcusage;
	ReturnSetInfo rsinfo;
	HeapTupleData tmptup;
	MemoryContext callerContext;
	bool		first_time = true;

	/*
	 * Execute per-tablefunc actions in appropriate context.
	 *
	 * The FunctionCallInfo needs to live across all the calls to a
	 * ValuePerCall function, so it can't be allocated in the per-tuple
	 * context. Similarly, the function arguments need to be evaluated in a
	 * context that is longer lived than the per-tuple context: The argument
	 * values would otherwise disappear when we reset that context in the
	 * inner loop.  As the caller's CurrentMemoryContext is typically a
	 * query-lifespan context, we don't want to leak memory there.  We require
	 * the caller to pass a separate memory context that can be used for this,
	 * and can be reset each time through to avoid bloat.
	 */
	MemoryContextReset(argContext);
	callerContext = MemoryContextSwitchTo(argContext);

	funcrettype = exprType((Node *) setexpr->expr);

	returnsTuple = type_is_rowtype(funcrettype);

	/*
	 * Prepare a resultinfo node for communication.  We always do this even if
	 * not expecting a set result, so that we can pass expectedDesc.  In the
	 * generic-expression case, the expression doesn't actually get to see the
	 * resultinfo, but set it up anyway because we use some of the fields as
	 * our own state variables.
	 */
	rsinfo.type = T_ReturnSetInfo;
	rsinfo.econtext = econtext;
	rsinfo.expectedDesc = expectedDesc;
	rsinfo.allowedModes = (int) (SFRM_ValuePerCall | SFRM_Materialize | SFRM_Materialize_Preferred);
	if (randomAccess)
		rsinfo.allowedModes |= (int) SFRM_Materialize_Random;
	rsinfo.returnMode = SFRM_ValuePerCall;
	/* isDone is filled below */
	rsinfo.setResult = NULL;
	rsinfo.setDesc = NULL;