Function EvalOrderByExpressions

src/backend/executor/nodeIndexscan.c:363–384

* Calculate the expressions in the ORDER BY clause, based on the heap tuple. */

 * Calculate the expressions in the ORDER BY clause, based on the heap tuple.
 */
static void
EvalOrderByExpressions(IndexScanState *node, ExprContext *econtext)
{
	int			i;
	ListCell   *l;
	MemoryContext oldContext;

	oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);

	i = 0;
	foreach(l, node->indexorderbyorig)
	{
		ExprState  *orderby = (ExprState *) lfirst(l);

		node->iss_OrderByValues[i] = ExecEvalExpr(orderby,
												  econtext,
												  &node->iss_OrderByNulls[i]);
		i++;
	}

	MemoryContextSwitchTo(oldContext);
}

/*
 * IndexRecheck -- access method routine to recheck a tuple in EvalPlanQual