Function ExecInitTableFunction

src/backend/executor/nodeTableFunction.c:248–451

* ExecInitTableFunction - Setup the table function executor */

 * ExecInitTableFunction - Setup the table function executor 
 */
TableFunctionState *
ExecInitTableFunction(TableFunctionScan *node, EState *estate, int eflags)
{
	TableFunctionState	*scanstate;
	PlanState           *subplan;
	Oid					 funcrettype;
	TypeFuncClass		 functypclass;
	RangeTblFunction *rtfunc;
	FuncExpr            *func;
	ExprContext         *econtext;
	TupleDesc            inputdesc  = NULL;
	TupleDesc			 resultdesc = NULL;
	ListCell   *lc;
	List	   *argstates;

	/* Inner plan is not used, outer plan must be present */
	Assert(innerPlan(node) == NULL);
	Assert(outerPlan(node) != NULL);

	/* Forward scan only */
	Assert(!(eflags & (EXEC_FLAG_MARK | EXEC_FLAG_BACKWARD)));

	/*
	 * Create state structure.
	 */
	scanstate = makeNode(TableFunctionState);
	scanstate->ss.ps.plan  = (Plan *)node;
	scanstate->ss.ps.state = estate;
	scanstate->ss.ps.ExecProcNode = ExecTableFunction;
	scanstate->inputscan   = palloc0(sizeof(AnyTableData));
	scanstate->is_firstcall = true;

	/* Create expression context for the node. */
	ExecAssignExprContext(estate, &scanstate->ss.ps);
	econtext = scanstate->ss.ps.ps_ExprContext;

	/* Initialize child nodes */
	outerPlanState(scanstate) = ExecInitNode(outerPlan(node), estate, eflags);
	subplan   = outerPlanState(scanstate);
	inputdesc = CreateTupleDescCopy(ExecGetResultType(subplan));

	/* 
	 * The funcexpr must be a function call.  This check is to verify that
	 * the planner didn't try to perform constant folding or other inlining
	 * on a function invoked as a table function.
	 */
	rtfunc = node->function;
	if (!rtfunc->funcexpr || !IsA(rtfunc->funcexpr, FuncExpr))
	{
		/* should not be possible */
		elog(ERROR, "table function expression is not a function expression");
	}
	func = (FuncExpr *) rtfunc->funcexpr;
	functypclass = get_expr_result_type((Node*) func, &funcrettype, &resultdesc);
	
	switch (functypclass)
	{
		case TYPEFUNC_COMPOSITE: