Function transformSortClause

src/backend/parser/parse_clause.c:2818–2845

* transformSortClause - * transform an ORDER BY clause * * ORDER BY items will be added to the targetlist (as resjunk columns) * if not already present, so the targetlist must be passed by reference. * * This is also used for window and aggregate ORDER BY clauses (which act * almost the same, but are always interpreted per SQL99 rules). */

 * almost the same, but are always interpreted per SQL99 rules).
 */
List *
transformSortClause(ParseState *pstate,
					List *orderlist,
					List **targetlist,
					ParseExprKind exprKind,
					bool useSQL99)
{
	List	   *sortlist = NIL;
	ListCell   *olitem;

	foreach(olitem, orderlist)
	{
		SortBy	   *sortby = (SortBy *) lfirst(olitem);
		TargetEntry *tle;

		if (useSQL99)
			tle = findTargetlistEntrySQL99(pstate, sortby->node,
										   targetlist, exprKind);
		else
			tle = findTargetlistEntrySQL92(pstate, sortby->node,
										   targetlist, exprKind);

		sortlist = addTargetToSortList(pstate, tle,
									   sortlist, *targetlist, sortby);
	}

	return sortlist;
}

/*
 * transformWindowDefinitions -