diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/plan/planner.c | 28 |
1 files changed, 16 insertions, 12 deletions
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 6d6978dcf5b..27d7b3dea26 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 1.228 2008/03/27 19:06:14 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.229 2008/03/28 02:00:11 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -835,6 +835,21 @@ grouping_planner(PlannerInfo *root, double tuple_fraction) MemSet(&agg_counts, 0, sizeof(AggClauseCounts)); + /* + * If the query involves ungrouped aggregation, then it can produce + * at most one row, so we can ignore any ORDER BY or DISTINCT + * request. This isn't all that exciting as an optimization, but it + * prevents a corner case when optimize_minmax_aggregates succeeds: + * if ORDER BY or DISTINCT were present we'd try, and fail, to match + * the EquivalenceClasses we're about to build with the modified + * targetlist entries it will create. + */ + if (parse->hasAggs && parse->groupClause == NIL) + { + parse->sortClause = NIL; + parse->distinctClause = NIL; + } + /* Preprocess targetlist */ tlist = preprocess_targetlist(root, tlist); @@ -950,17 +965,6 @@ grouping_planner(PlannerInfo *root, double tuple_fraction) * right tlist, and it has no sort order. */ current_pathkeys = NIL; - /* - * In fact, since we don't optimize grouped aggregates, it - * needs no sort order --- there must be exactly one output row, - * and so any ORDER BY or DISTINCT attached to the query is - * useless and can be dropped. Aside from saving useless cycles, - * this protects us against problems with matching the hacked-up - * tlist entries to sort clauses. - */ - Assert(!parse->groupClause); - parse->sortClause = NULL; - parse->distinctClause = NULL; } else { |