diff options
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 44 |
1 files changed, 42 insertions, 2 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 4b09f03e6e7..25bd55dadf3 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.133 2005/06/09 04:18:59 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.134 2005/06/10 03:32:21 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -353,6 +353,28 @@ set_inherited_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, set_cheapest(rel); } +/* quick-and-dirty test to see if any joining is needed */ +static bool +has_multiple_baserels(PlannerInfo *root) +{ + int num_base_rels = 0; + Index rti; + + for (rti = 1; rti < root->base_rel_array_size; rti++) + { + RelOptInfo *brel = root->base_rel_array[rti]; + + if (brel == NULL) + continue; + + /* ignore RTEs that are "other rels" */ + if (brel->reloptkind == RELOPT_BASEREL) + if (++num_base_rels > 1) + return true; + } + return false; +} + /* * set_subquery_pathlist * Build the (single) access path for a subquery RTE @@ -361,8 +383,10 @@ static void set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel, Index rti, RangeTblEntry *rte) { + Query *parse = root->parse; Query *subquery = rte->subquery; bool *differentTypes; + double tuple_fraction; List *pathkeys; List *subquery_pathkeys; @@ -416,8 +440,24 @@ set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel, pfree(differentTypes); + /* + * We can safely pass the outer tuple_fraction down to the subquery + * if the outer level has no joining, aggregation, or sorting to do. + * Otherwise we'd better tell the subquery to plan for full retrieval. + * (XXX This could probably be made more intelligent ...) + */ + if (parse->hasAggs || + parse->groupClause || + parse->havingQual || + parse->distinctClause || + parse->sortClause || + has_multiple_baserels(root)) + tuple_fraction = 0.0; /* default case */ + else + tuple_fraction = root->tuple_fraction; + /* Generate the plan for the subquery */ - rel->subplan = subquery_planner(subquery, 0.0 /* default case */, + rel->subplan = subquery_planner(subquery, tuple_fraction, &subquery_pathkeys); /* Copy number of output rows from subplan */ |