diff options
Diffstat (limited to 'src/backend/optimizer/util/pathnode.c')
| -rw-r--r-- | src/backend/optimizer/util/pathnode.c | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c index 20d8074bce4..231d221b21e 100644 --- a/src/backend/optimizer/util/pathnode.c +++ b/src/backend/optimizer/util/pathnode.c @@ -694,6 +694,35 @@ create_merge_append_path(PlannerInfo *root, pathnode->path.pathkeys = pathkeys; pathnode->subpaths = subpaths; + /* + * Apply query-wide LIMIT if known and path is for sole base relation. + * Finding out the latter at this low level is a bit klugy. + */ + pathnode->limit_tuples = root->limit_tuples; + if (pathnode->limit_tuples >= 0) + { + Index rti; + + for (rti = 1; rti < root->simple_rel_array_size; rti++) + { + RelOptInfo *brel = root->simple_rel_array[rti]; + + if (brel == NULL) + continue; + + /* ignore RTEs that are "other rels" */ + if (brel->reloptkind != RELOPT_BASEREL) + continue; + + if (brel != rel) + { + /* Oops, it's a join query */ + pathnode->limit_tuples = -1.0; + break; + } + } + } + /* Add up all the costs of the input paths */ input_startup_cost = 0; input_total_cost = 0; @@ -720,7 +749,7 @@ create_merge_append_path(PlannerInfo *root, subpath->parent->width, 0.0, work_mem, - -1.0); + pathnode->limit_tuples); input_startup_cost += sort_path.startup_cost; input_total_cost += sort_path.total_cost; } |