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help / color / mirror / Atom feedFrom: Peter Geoghegan <pg@bowt.ie>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix another empty nbtree index SSI race.
Date: Sat, 25 Jul 2026 16:01:57 +0000
Message-ID: <E1wnep3-00000000GoK-3ify@gemulon.postgresql.org> (raw)
Fix another empty nbtree index SSI race.
Commit f9b7fc65 fixed a race when predicate-locking completely empty
btrees: without a buffer lock held, a matching key could be inserted
between _bt_search and the PredicateLockRelation call, so the scan would
miss concurrently inserted tuples while the writer wouldn't see the
reader's predicate lock. That commit only fixed _bt_first's _bt_search
path, though. Scans without useful insertion scan keys return early
from _bt_first via _bt_endpoint, which still didn't recheck if the
relation was empty.
To fix, add handling to _bt_endpoint that is analogous to the handling
added to _bt_search by commit f9b7fc65.
Author: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAH2-WzkNoTn3yXY0iGkSuavJ+sL8EROf+kitW+_2v2tJVWuKmA@mail.gmail.com
Backpatch-through: 14
Branch
------
REL_18_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/d560e730e813343b8d3f4a336244f2bc09ca84fc
Modified Files
--------------
src/backend/access/nbtree/nbtsearch.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: pg@bowt.ie, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix another empty nbtree index SSI race.
In-Reply-To: <E1wnep3-00000000GoK-3ify@gemulon.postgresql.org>
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