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help / color / mirror / Atom feedFrom: Richard Guo <[email protected]>
To: [email protected]
Subject: pgsql: Fix wrong unsafe-flag test in check_output_expressions()
Date: Wed, 03 Jun 2026 00:43:32 +0000
Message-ID: <[email protected]> (raw)
Fix wrong unsafe-flag test in check_output_expressions()
The check for window functions (point 4) guarded on the wrong bit: it
tested UNSAFE_NOTIN_DISTINCTON_CLAUSE while setting
UNSAFE_NOTIN_PARTITIONBY_CLAUSE. Each check in this loop guards on
the same bit it is about to set, as an idempotency optimization, since
unsafeFlags[] is accumulated across the arms of a set operation and
there is no point recomputing a column's status once its bit is
present.
This is not a live bug. When UNSAFE_NOTIN_PARTITIONBY_CLAUSE is
already set but UNSAFE_NOTIN_DISTINCTON_CLAUSE is not, the guard fails
to skip targetIsInAllPartitionLists() and recomputes it, but setting
the same bit again changes nothing. When
UNSAFE_NOTIN_DISTINCTON_CLAUSE is already set, point 4 is skipped and
UNSAFE_NOTIN_PARTITIONBY_CLAUSE is left unset; but such a column is
already unsafe for pushdown via UNSAFE_NOTIN_DISTINCTON_CLAUSE, so the
outcome is unchanged.
To fix, test UNSAFE_NOTIN_PARTITIONBY_CLAUSE, matching the bit being
set and the pattern of the surrounding checks.
Back-patch to v15, where the buggy check was introduced.
Author: Richard Guo <[email protected]>
Reviewed-by: Tender Wang <[email protected]>
Reviewed-by: David Rowley <[email protected]>
Discussion: https://postgr.es/m/CAMbWs49Q_xnF_P2QSUyDzJ34MnrO7dh-cUAaK2HJPgSgh88NcA@mail.gmail.com
Backpatch-through: 15
Branch
------
REL_15_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/919471ead95ff13e7708a290c0c6bdd7a494f640
Modified Files
--------------
src/backend/optimizer/path/allpaths.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
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