diff options
Diffstat (limited to 'src/backend/optimizer/plan/planmain.c')
| -rw-r--r-- | src/backend/optimizer/plan/planmain.c | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c index a9747b32799..1a923a506ff 100644 --- a/src/backend/optimizer/plan/planmain.c +++ b/src/backend/optimizer/plan/planmain.c @@ -14,7 +14,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.61 2000/10/05 19:11:29 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.62 2000/11/12 00:36:58 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -65,7 +65,8 @@ static Plan *subplanner(Query *root, List *flat_tlist, * tuple_fraction >= 1: tuple_fraction is the absolute number of tuples * expected to be retrieved (ie, a LIMIT specification) * Note that while this routine and its subroutines treat a negative - * tuple_fraction the same as 0, union_planner has a different interpretation. + * tuple_fraction the same as 0, grouping_planner has a different + * interpretation. * * Returns a query plan. *-------------------- @@ -125,9 +126,16 @@ query_planner(Query *root, subplan = subplanner(root, var_only_tlist, tuple_fraction); /* - * Build a result node to control the plan if we have constant quals. + * Build a result node to control the plan if we have constant quals, + * or if the top-level plan node is one that cannot do expression + * evaluation (it won't be able to evaluate the requested tlist). + * Currently, the only plan node we might see here that falls into + * that category is Append. + * + * XXX future improvement: if the given tlist is flat anyway, we don't + * really need a Result node. */ - if (constant_quals) + if (constant_quals || IsA(subplan, Append)) { /* @@ -325,8 +333,8 @@ subplanner(Query *root, /* * Nothing for it but to sort the cheapest-total-cost path --- but we - * let the caller do that. union_planner has to be able to add a sort - * node anyway, so no need for extra code here. (Furthermore, the + * let the caller do that. grouping_planner has to be able to add a + * sort node anyway, so no need for extra code here. (Furthermore, the * given pathkeys might involve something we can't compute here, such * as an aggregate function...) */ |