diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 000d757bdd..781916f219 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -4423,6 +4423,7 @@ create_one_window_path(PlannerInfo *root,
 	PathTarget *window_target;
 	ListCell   *l;
 	List	   *topqual = NIL;
+	bool		has_runcondition = false;
 
 	/*
 	 * Since each window clause could require a different sort order, we stack
@@ -4457,6 +4458,42 @@ create_one_window_path(PlannerInfo *root,
 												path->pathkeys,
 												&presorted_keys);
 
+		has_runcondition |= (wc->runCondition != NIL);
+
+		/*
+		 * If not sorted already and the query has an ORDER BY clause, then we
+		 * try to push the entire ORDER BY below the final WindowAgg.  We
+		 * don't do this when the query has a DISTINCT clause as the planner
+		 * might opt to do a Hash Aggregate and spoil our efforts here.  We
+		 * also can't do this when the ORDER BY contains any WindowFuncs as we
+		 * obviously can't sort something that's yet to be evaluated.  We also
+		 * don't bother with this when there is a WindowClauses with a
+		 * runCondition as those can reduce the number of rows to sort in the
+		 * ORDER BY and we don't want add complexity to the WindowAgg sort if
+		 * the final ORDER BY sort is going to have far fewer rows to sort.
+		 * For the same reason, don't bother if the query has a LIMIT clause.
+		 */
+		if (!is_sorted && lnext(activeWindows, l) == NULL &&
+			root->parse->distinctClause == NIL &&
+			root->parse->sortClause != NIL &&
+			!has_runcondition && root->parse->limitCount == NULL &&
+			!contain_window_function((Node *) get_sortgrouplist_exprs(root->parse->sortClause,
+																	  root->processed_tlist)))
+		{
+			List	   *orderby_pathkeys;
+
+			orderby_pathkeys = make_pathkeys_for_sortclauses(root,
+															 root->parse->sortClause,
+															 root->processed_tlist);
+
+			if (pathkeys_contained_in(window_pathkeys, orderby_pathkeys))
+				window_pathkeys = orderby_pathkeys;
+
+			is_sorted = pathkeys_count_contained_in(window_pathkeys,
+													path->pathkeys,
+													&presorted_keys);
+		}
+
 		/* Sort if necessary */
 		if (!is_sorted)
 		{