diff options
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 43f4e757487..c4e4db15a68 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -479,13 +479,20 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, } /* - * If this is a baserel, consider gathering any partial paths we may have - * created for it. (If we tried to gather inheritance children, we could + * If this is a baserel, we should normally consider gathering any partial + * paths we may have created for it. + * + * However, if this is an inheritance child, skip it. Otherwise, we could * end up with a very large number of gather nodes, each trying to grab - * its own pool of workers, so don't do this for otherrels. Instead, - * we'll consider gathering partial paths for the parent appendrel.) + * its own pool of workers. Instead, we'll consider gathering partial + * paths for the parent appendrel. + * + * Also, if this is the topmost scan/join rel (that is, the only baserel), + * we postpone this until the final scan/join targelist is available (see + * grouping_planner). */ - if (rel->reloptkind == RELOPT_BASEREL) + if (rel->reloptkind == RELOPT_BASEREL && + bms_membership(root->all_baserels) != BMS_SINGLETON) generate_gather_paths(root, rel, false); /* @@ -2699,8 +2706,13 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels) /* Create paths for partitionwise joins. */ generate_partitionwise_join_paths(root, rel); - /* Create GatherPaths for any useful partial paths for rel */ - generate_gather_paths(root, rel, false); + /* + * Except for the topmost scan/join rel, consider gathering + * partial paths. We'll do the same for the topmost scan/join rel + * once we know the final targetlist (see grouping_planner). + */ + if (lev < levels_needed) + generate_gather_paths(root, rel, false); /* Find and save the cheapest paths for this rel */ set_cheapest(rel); |