Function ValuesNext

src/backend/executor/nodeValuesscan.c:49–177

---------------------------------------------------------------- * ValuesNext * * This is a workhorse for ExecValuesScan * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ValuesNext(ValuesScanState *node)
{
	TupleTableSlot *slot;
	EState	   *estate;
	ExprContext *econtext;
	ScanDirection direction;
	int			curr_idx;

	/*
	 * get information from the estate and scan state
	 */
	estate = node->ss.ps.state;
	direction = estate->es_direction;
	slot = node->ss.ss_ScanTupleSlot;
	econtext = node->rowcontext;

	/*
	 * Get the next tuple. Return NULL if no more tuples.
	 */
	if (ScanDirectionIsForward(direction))
	{
		if (node->curr_idx < node->array_len)
			node->curr_idx++;
	}
	else
	{
		if (node->curr_idx >= 0)
			node->curr_idx--;
	}

	/*
	 * Always clear the result slot; this is appropriate if we are at the end
	 * of the data, and if we're not, we still need it as the first step of
	 * the store-virtual-tuple protocol.  It seems wise to clear the slot
	 * before we reset the context it might have pointers into.
	 */
	ExecClearTuple(slot);

	curr_idx = node->curr_idx;
	if (curr_idx >= 0 && curr_idx < node->array_len)
	{
		List	   *exprlist = node->exprlists[curr_idx];
		List	   *exprstatelist = node->exprstatelists[curr_idx];
		MemoryContext oldContext;
		Datum	   *values;
		bool	   *isnull;
		ListCell   *lc;
		int			resind;

		/*
		 * Get rid of any prior cycle's leftovers.  We use ReScanExprContext
		 * not just ResetExprContext because we want any registered shutdown
		 * callbacks to be called.
		 */
		ReScanExprContext(econtext);

		/*