Repair optimization bug I introduced in a moment of brain fade back in

Nov 2002: when constant-expression simplification removes all the
aggregate function calls from a query, that doesn't mean we can act as
though there never were any aggregates.  Per bug report from Gabor Szucs.

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index e00f73c74b1c84f53485f01269a98a69fa023d58..fea7e4fef131fa20873bd6a2c20078cddadb0099 100644 (file)
--- 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 1.166 2004/02/03 17:34:03 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.167 2004/02/13 22:26:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -709,19 +709,18 @@ grouping_planner(Query *parse, double tuple_fraction)
 
                /*
                 * Will need actual number of aggregates for estimating costs.
-                * Also, it's possible that optimization has eliminated all
-                * aggregates, and we may as well check for that here.
                 *
                 * Note: we do not attempt to detect duplicate aggregates here; a
                 * somewhat-overestimated count is okay for our present purposes.
+                *
+                * Note: think not that we can turn off hasAggs if we find no aggs.
+                * It is possible for constant-expression simplification to remove
+                * all explicit references to aggs, but we still have to follow the
+                * aggregate semantics (eg, producing only one output row).
                 */
                if (parse->hasAggs)
-               {
                        numAggs = count_agg_clause((Node *) tlist) +
                                count_agg_clause(parse->havingQual);
-                       if (numAggs == 0)
-                               parse->hasAggs = false;
-               }
 
                /*
                 * Figure out whether we need a sorted result from query_planner.