Fix EquivalenceClass code to handle volatile sort expressions in a more

predictable manner; in particular that if you say ORDER BY output-column-ref,
it will in fact sort by that specific column even if there are multiple
syntactic matches.  An example is
	SELECT random() AS a, random() AS b FROM ... ORDER BY b, a;
While the use-case for this might be a bit debatable, it worked as expected
in earlier releases, so we should preserve the behavior for 8.3.  Per my
recent proposal.

While at it, fix convert_subquery_pathkeys() to handle RelabelType stripping
in both directions; it needs this for the same reasons make_sort_from_pathkeys
does.

1 files changed, 22 insertions, 11 deletions

diff --git a/src/backend/optimizer/util/tlist.c b/src/backend/optimizer/util/tlist.c
index e58fe7dc7f1..d2ac14cfa1b 100644
--- a/src/backend/optimizer/util/tlist.c
+++ b/src/backend/optimizer/util/tlist.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/tlist.c,v 1.75 2007/11/08 19:25:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/tlist.c,v 1.76 2007/11/08 21:49:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -131,26 +131,22 @@ add_to_flat_tlist(List *tlist, List *vars)
 	return tlist;
 }
 
+
 /*
- * get_sortgroupclause_tle
- *		Find the targetlist entry matching the given SortClause
- *		(or GroupClause) by ressortgroupref, and return it.
- *
- * Because GroupClause is typedef'd as SortClause, either kind of
- * node can be passed without casting.
+ * get_sortgroupref_tle
+ *		Find the targetlist entry matching the given SortGroupRef index,
+ *		and return it.
  */
 TargetEntry *
-get_sortgroupclause_tle(SortClause *sortClause,
-						List *targetList)
+get_sortgroupref_tle(Index sortref, List *targetList)
 {
-	Index		refnumber = sortClause->tleSortGroupRef;
 	ListCell   *l;
 
 	foreach(l, targetList)
 	{
 		TargetEntry *tle = (TargetEntry *) lfirst(l);
 
-		if (tle->ressortgroupref == refnumber)
+		if (tle->ressortgroupref == sortref)
 			return tle;
 	}
 
@@ -159,6 +155,21 @@ get_sortgroupclause_tle(SortClause *sortClause,
 }
 
 /*
+ * get_sortgroupclause_tle
+ *		Find the targetlist entry matching the given SortClause
+ *		(or GroupClause) by ressortgroupref, and return it.
+ *
+ * Because GroupClause is typedef'd as SortClause, either kind of
+ * node can be passed without casting.
+ */
+TargetEntry *
+get_sortgroupclause_tle(SortClause *sortClause,
+						List *targetList)
+{
+	return get_sortgroupref_tle(sortClause->tleSortGroupRef, targetList);
+}
+
+/*
  * get_sortgroupclause_expr
  *		Find the targetlist entry matching the given SortClause
  *		(or GroupClause) by ressortgroupref, and return its expression.