diff options
Diffstat (limited to 'src/backend/optimizer/util/pathnode.c')
| -rw-r--r-- | src/backend/optimizer/util/pathnode.c | 34 |
1 files changed, 30 insertions, 4 deletions
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c index 94109ee01e3..a2a6b35cd32 100644 --- a/src/backend/optimizer/util/pathnode.c +++ b/src/backend/optimizer/util/pathnode.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/util/pathnode.c,v 1.97 2004/01/05 05:07:35 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/util/pathnode.c,v 1.98 2004/01/05 18:04:39 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -20,12 +20,14 @@ #include "executor/executor.h" #include "miscadmin.h" #include "nodes/plannodes.h" +#include "optimizer/clauses.h" #include "optimizer/cost.h" #include "optimizer/pathnode.h" #include "optimizer/paths.h" #include "optimizer/restrictinfo.h" #include "parser/parse_expr.h" #include "parser/parse_oper.h" +#include "parser/parsetree.h" #include "utils/memutils.h" #include "utils/selfuncs.h" #include "utils/syscache.h" @@ -547,6 +549,30 @@ create_unique_path(Query *root, RelOptInfo *rel, Path *subpath) pathnode->subpath = subpath; /* + * If the input is a subquery that uses DISTINCT, we don't need to do + * anything; its output is already unique. (Are there any other cases + * in which we can easily prove the input must be distinct?) + */ + if (rel->rtekind == RTE_SUBQUERY) + { + RangeTblEntry *rte = rt_fetch(rel->relid, root->rtable); + Query *subquery = rte->subquery; + + if (has_distinct_clause(subquery)) + { + pathnode->umethod = UNIQUE_PATH_NOOP; + pathnode->rows = rel->rows; + pathnode->path.startup_cost = subpath->startup_cost; + pathnode->path.total_cost = subpath->total_cost; + pathnode->path.pathkeys = subpath->pathkeys; + + rel->cheapest_unique_path = (Path *) pathnode; + + return pathnode; + } + } + + /* * Try to identify the targetlist that will actually be unique-ified. * In current usage, this routine is only used for sub-selects of IN * clauses, so we should be able to find the tlist in in_info_list. @@ -599,7 +625,7 @@ create_unique_path(Query *root, RelOptInfo *rel, Path *subpath) * compare costs. We only try this if we know the targetlist for sure * (else we can't be sure about the datatypes involved). */ - pathnode->use_hash = false; + pathnode->umethod = UNIQUE_PATH_SORT; if (enable_hashagg && sub_targetlist && hash_safe_tlist(sub_targetlist)) { /* @@ -617,11 +643,11 @@ create_unique_path(Query *root, RelOptInfo *rel, Path *subpath) subpath->total_cost, rel->rows); if (agg_path.total_cost < sort_path.total_cost) - pathnode->use_hash = true; + pathnode->umethod = UNIQUE_PATH_HASH; } } - if (pathnode->use_hash) + if (pathnode->umethod == UNIQUE_PATH_HASH) { pathnode->path.startup_cost = agg_path.startup_cost; pathnode->path.total_cost = agg_path.total_cost; |