diff options
| author | Tomas Vondra <tomas.vondra@postgresql.org> | 2020-11-03 20:07:23 +0100 |
|---|---|---|
| committer | Tomas Vondra <tomas.vondra@postgresql.org> | 2020-11-03 22:31:57 +0100 |
| commit | ebb7ae839d033d0f279670e249f54646a08b8c48 (patch) | |
| tree | 96921a9a470206f6df84d4072f6d0fc2dc18b7fe /src/backend/optimizer/path/allpaths.c | |
| parent | 92f87182f2c617fd420832972b6d0ae4527301c8 (diff) | |
| download | postgresql-ebb7ae839d033d0f279670e249f54646a08b8c48.tar.gz postgresql-ebb7ae839d033d0f279670e249f54646a08b8c48.zip | |
Fix get_useful_pathkeys_for_relation for volatile expressions
When considering Incremental Sort below a Gather Merge, we need to be
a bit more careful when matching pathkeys to EC members. It's not enough
to find a member whose Vars are all in the current relation's target;
volatile expressions in particular need to be contained in the target,
otherwise it's too early to use the pathkey.
Reported-by: Jaime Casanova
Author: James Coleman
Reviewed-by: Tomas Vondra
Backpatch-through: 13, where the incremental sort code was added
Discussion: https://postgr.es/m/CAJGNTeNaxpXgBVcRhJX%2B2vSbq%2BF2kJqGBcvompmpvXb7pq%2BoFA%40mail.gmail.com
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 8ad6384c6ae..84a69b064a9 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -2816,7 +2816,8 @@ get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel) /* * Considering query_pathkeys is always worth it, because it might allow * us to avoid a total sort when we have a partially presorted path - * available. + * available or to push the total sort into the parallel portion of the + * query. */ if (root->query_pathkeys) { @@ -2829,17 +2830,17 @@ get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel) EquivalenceClass *pathkey_ec = pathkey->pk_eclass; /* - * We can only build an Incremental Sort for pathkeys which - * contain an EC member in the current relation, so ignore any - * suffix of the list as soon as we find a pathkey without an EC - * member the relation. + * We can only build a sort for pathkeys which contain an EC + * member in the current relation's target, so ignore any suffix + * of the list as soon as we find a pathkey without an EC member + * in the relation. * * By still returning the prefix of the pathkeys list that does * meet criteria of EC membership in the current relation, we * enable not just an incremental sort on the entirety of * query_pathkeys but also incremental sort below a JOIN. */ - if (!find_em_expr_for_rel(pathkey_ec, rel)) + if (!find_em_expr_usable_for_sorting_rel(pathkey_ec, rel)) break; npathkeys++; |