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| author | Robert Haas <rhaas@postgresql.org> | 2016-06-09 12:40:23 -0400 |
|---|---|---|
| committer | Robert Haas <rhaas@postgresql.org> | 2016-06-09 12:43:36 -0400 |
| commit | b12fd41c695b43c76b0a9a4d19ba43b05536440c (patch) | |
| tree | 966a7ca8b9c268b70f38257a56aeccaa25fd82b2 /src/backend/optimizer/path/allpaths.c | |
| parent | e7bcd983f56136a9580076b60d5c19eb2fd83301 (diff) | |
| download | postgresql-b12fd41c695b43c76b0a9a4d19ba43b05536440c.tar.gz postgresql-b12fd41c695b43c76b0a9a4d19ba43b05536440c.zip | |
Don't generate parallel paths for rels with parallel-restricted outputs.
Such paths are unsafe. To make it cheaper to detect when this case
applies, track whether a relation's default PathTarget contains any
non-Vars. In most cases, the answer will be no, which enables us to
determine cheaply that the target list for a proposed path is
parallel-safe. However, subquery pull-up can create cases that
require us to inspect the target list more carefully.
Amit Kapila, reviewed by me.
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index cf6a9a9f82a..6deb2cf0c9c 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -608,6 +608,15 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel, if (has_parallel_hazard((Node *) rel->baserestrictinfo, false)) return; + /* + * If the relation's outputs are not parallel-safe, we must give up. + * In the common case where the relation only outputs Vars, this check is + * very cheap; otherwise, we have to do more work. + */ + if (rel->reltarget_has_non_vars && + has_parallel_hazard((Node *) rel->reltarget->exprs, false)) + return; + /* We have a winner. */ rel->consider_parallel = true; } @@ -971,6 +980,7 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel, adjust_appendrel_attrs(root, (Node *) rel->reltarget->exprs, appinfo); + childrel->reltarget_has_non_vars = rel->reltarget_has_non_vars; /* * We have to make child entries in the EquivalenceClass data |