diff options
Diffstat (limited to 'src/backend/optimizer/plan/planner.c')
| -rw-r--r-- | src/backend/optimizer/plan/planner.c | 31 |
1 files changed, 22 insertions, 9 deletions
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)) { |