3 files changed, 53 insertions, 14 deletions

diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c
index 3776cf9b347..d25a5509b4c 100644
--- a/src/backend/optimizer/plan/planmain.c
+++ b/src/backend/optimizer/plan/planmain.c
@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planmain.c,v 1.106 2008/01/11 04:02:18 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planmain.c,v 1.107 2008/07/31 22:47:56 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -288,7 +288,7 @@ query_planner(PlannerInfo *root, List *tlist,
 		 * levels of sort --- and, therefore, certainly need to read all the
 		 * tuples --- unless ORDER BY is a subset of GROUP BY.
 		 */
-		if (parse->groupClause && parse->sortClause &&
+		if (root->group_pathkeys && root->sort_pathkeys &&
 			!pathkeys_contained_in(root->sort_pathkeys, root->group_pathkeys))
 			tuple_fraction = 0.0;
 	}
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 9248022d8b3..6ebbc5b7bc3 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.234 2008/07/10 02:14:03 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.235 2008/07/31 22:47:56 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -826,6 +826,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 		/*
 		 * Calculate pathkeys that represent result ordering requirements
 		 */
+		Assert(parse->distinctClause == NIL);
 		sort_pathkeys = make_pathkeys_for_sortclauses(root,
 													  parse->sortClause,
 													  tlist,
@@ -864,17 +865,29 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 		 * Calculate pathkeys that represent grouping/ordering requirements.
 		 * Stash them in PlannerInfo so that query_planner can canonicalize
 		 * them after EquivalenceClasses have been formed.
+		 *
+		 * Note: for the moment, DISTINCT is always implemented via sort/uniq,
+		 * and we set the sort_pathkeys to be the more rigorous of the
+		 * DISTINCT and ORDER BY requirements.  This should be changed
+		 * someday, but DISTINCT ON is a bit of a problem ...
 		 */
 		root->group_pathkeys =
 			make_pathkeys_for_sortclauses(root,
 										  parse->groupClause,
 										  tlist,
 										  false);
-		root->sort_pathkeys =
-			make_pathkeys_for_sortclauses(root,
-										  parse->sortClause,
-										  tlist,
-										  false);
+		if (list_length(parse->distinctClause) > list_length(parse->sortClause))
+			root->sort_pathkeys =
+				make_pathkeys_for_sortclauses(root,
+											  parse->distinctClause,
+											  tlist,
+											  false);
+		else
+			root->sort_pathkeys =
+				make_pathkeys_for_sortclauses(root,
+											  parse->sortClause,
+											  tlist,
+											  false);
 
 		/*
 		 * Will need actual number of aggregates for estimating costs.
@@ -903,9 +916,9 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 		 * by ORDER BY --- but that might just leave us failing to exploit an
 		 * available sort order at all. Needs more thought...)
 		 */
-		if (parse->groupClause)
+		if (root->group_pathkeys)
 			root->query_pathkeys = root->group_pathkeys;
-		else if (parse->sortClause)
+		else if (root->sort_pathkeys)
 			root->query_pathkeys = root->sort_pathkeys;
 		else
 			root->query_pathkeys = NIL;
@@ -1172,7 +1185,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
 	 * If we were not able to make the plan come out in the right order, add
 	 * an explicit sort step.
 	 */
-	if (parse->sortClause)
+	if (sort_pathkeys)
 	{
 		if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
 		{
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index ed18cf5e3fe..b30cedee9fc 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.147 2008/06/19 00:46:04 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.148 2008/07/31 22:47:56 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -69,6 +69,7 @@ static List *generate_setop_tlist(List *colTypes, int flag,
 static List *generate_append_tlist(List *colTypes, bool flag,
 					  List *input_plans,
 					  List *refnames_tlist);
+static List *generate_setop_sortlist(List *targetlist);
 static void expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte,
 						 Index rti);
 static void make_inh_translation_lists(Relation oldrelation,
@@ -319,7 +320,7 @@ generate_union_plan(SetOperationStmt *op, PlannerInfo *root,
 	{
 		List	   *sortList;
 
-		sortList = addAllTargetsToSortList(NULL, NIL, tlist, false);
+		sortList = generate_setop_sortlist(tlist);
 		if (sortList)
 		{
 			plan = (Plan *) make_sort_from_sortclauses(root, sortList, plan);
@@ -384,7 +385,7 @@ generate_nonunion_plan(SetOperationStmt *op, PlannerInfo *root,
 	 * Sort the child results, then add a SetOp plan node to generate the
 	 * correct output.
 	 */
-	sortList = addAllTargetsToSortList(NULL, NIL, tlist, false);
+	sortList = generate_setop_sortlist(tlist);
 
 	if (sortList == NIL)		/* nothing to sort on? */
 	{
@@ -675,6 +676,31 @@ generate_append_tlist(List *colTypes, bool flag,
 	return tlist;
 }
 
+/*
+ * generate_setop_sortlist
+ *		Build a SortClause list enumerating all the non-resjunk tlist entries,
+ *		using default ordering properties.
+ */
+static List *
+generate_setop_sortlist(List *targetlist)
+{
+	List	   *sortlist = NIL;
+	ListCell   *l;
+
+	foreach(l, targetlist)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
+
+		if (!tle->resjunk)
+			sortlist = addTargetToSortList(NULL, tle,
+										   sortlist, targetlist,
+										   SORTBY_DEFAULT,
+										   SORTBY_NULLS_DEFAULT,
+										   NIL, false);
+	}
+	return sortlist;
+}
+
 
 /*
  * find_all_inheritors -