Teach planner how to propagate pathkeys from sub-SELECTs in FROM up to

the outer query.  (The implementation is a bit klugy, but it would take
nontrivial restructuring to make it nicer, which this is probably not
worth.)  This avoids unnecessary sort steps in examples like
SELECT foo,count(*) FROM (SELECT ... ORDER BY foo,bar) sub GROUP BY foo
which means there is now a reasonable technique for controlling the
order of inputs to custom aggregates, even in the grouping case.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 8a59730aef5..3984c666f51 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/pathnode.c,v 1.87 2003/02/08 20:20:55 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/pathnode.c,v 1.88 2003/02/15 20:12:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -676,13 +676,13 @@ hash_safe_tlist(List *tlist)
  *	  returning the pathnode.
  */
 Path *
-create_subqueryscan_path(RelOptInfo *rel)
+create_subqueryscan_path(RelOptInfo *rel, List *pathkeys)
 {
 	Path	   *pathnode = makeNode(Path);
 
 	pathnode->pathtype = T_SubqueryScan;
 	pathnode->parent = rel;
-	pathnode->pathkeys = NIL;	/* for now, assume unordered result */
+	pathnode->pathkeys = pathkeys;
 
 	/* just copy the subplan's cost estimates */
 	pathnode->startup_cost = rel->subplan->startup_cost;