Function ExecInitFunctionScan

src/backend/executor/nodeFunctionscan.c:360–637

---------------------------------------------------------------- * ExecInitFunctionScan * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
FunctionScanState *
ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
{
	FunctionScanState *scanstate;
	int			nfuncs = list_length(node->functions);
	TupleDesc	scan_tupdesc;
	int			i,
				natts;
	ListCell   *lc;

	/* check for unsupported flags */
	Assert(!(eflags & EXEC_FLAG_MARK));

	/*
	 * FunctionScan should not have any children.
	 */
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create new ScanState for node
	 */
	scanstate = makeNode(FunctionScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;
	scanstate->ss.ps.ExecProcNode = ExecFunctionScan;
	scanstate->eflags = eflags;
	scanstate->resultInTupleStore = node->resultInTupleStore;
	scanstate->initplanId = node->initplanId;
	scanstate->ts_state = NULL;

	/*
	 * are we adding an ordinality column?
	 */
	scanstate->ordinality = node->funcordinality;

	scanstate->nfuncs = nfuncs;
	if (nfuncs == 1 && !node->funcordinality)
		scanstate->simple = true;
	else
		scanstate->simple = false;

	/*
	 * Ordinal 0 represents the "before the first row" position.
	 *
	 * We need to track ordinal position even when not adding an ordinality
	 * column to the result, in order to handle backwards scanning properly
	 * with multiple functions with different result sizes. (We can't position
	 * any individual function's tuplestore any more than 1 place beyond its
	 * end, so when scanning backwards, we need to know when to start
	 * including the function in the scan again.)
	 */
	scanstate->ordinal = 0;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node