diff options
| author | Thomas Munro | 2019-06-18 10:38:30 +0000 |
|---|---|---|
| committer | Thomas Munro | 2019-06-18 13:25:57 +0000 |
| commit | aca127c105aae551620d607e88d76930e6b9a2cf (patch) | |
| tree | 0bfa491870fa91d9c93396589af251c4e3f27623 /src | |
| parent | 0ab7110bcbcce5ff58afb32e7871c54e87502139 (diff) | |
Prevent Parallel Hash Join for JOIN_UNIQUE_INNER.
WHERE EXISTS (...) queries cannot be executed by Parallel Hash Join
with jointype JOIN_UNIQUE_INNER, because there is no way to make a
partial plan totally unique. The consequence of allowing such plans
was duplicate results from some EXISTS queries.
Back-patch to 11. Bug #15857.
Author: Thomas Munro
Reviewed-by: Tom Lane
Reported-by: Vladimir Kriukov
Discussion: https://postgr.es/m/15857-d1ba2a64bce0795e%40postgresql.org
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/path/joinpath.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c index 501ad775cbe..dc28b56e742 100644 --- a/src/backend/optimizer/path/joinpath.c +++ b/src/backend/optimizer/path/joinpath.c @@ -1867,9 +1867,12 @@ hash_inner_and_outer(PlannerInfo *root, /* * Can we use a partial inner plan too, so that we can build a - * shared hash table in parallel? + * shared hash table in parallel? We can't handle + * JOIN_UNIQUE_INNER because we can't guarantee uniqueness. */ - if (innerrel->partial_pathlist != NIL && enable_parallel_hash) + if (innerrel->partial_pathlist != NIL && + save_jointype != JOIN_UNIQUE_INNER && + enable_parallel_hash) { cheapest_partial_inner = (Path *) linitial(innerrel->partial_pathlist); |