From: Peter Geoghegan <pg@bowt.ie>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix btmarkpos/btrestrpos array key wraparound bug.
Date: Thu, 28 Sep 2023 23:30:00 +0000
Message-ID: <E1qm0SG-006XJN-HU@gemulon.postgresql.org> (raw)
Fix btmarkpos/btrestrpos array key wraparound bug.
nbtree's mark/restore processing failed to correctly handle an edge case
involving array key advancement and related search-type scan key state.
Scans with ScalarArrayScalarArrayOpExpr quals requiring mark/restore
processing (for a merge join) could incorrectly conclude that an
affected array/scan key must not have advanced during the time between
marking and restoring the scan's position.
As a result of all this, array key handling within btrestrpos could skip
a required call to _bt_preprocess_keys(). This confusion allowed later
primitive index scans to overlook tuples matching the true current array
keys. The scan's search-type scan keys would still have spurious values
corresponding to the final array element(s) -- not values matching the
first/now-current array element(s).
To fix, remember that "array key wraparound" has taken place during the
ongoing btrescan in a flag variable stored in the scan's state, and use
that information at the point where btrestrpos decides if another call
to _bt_preprocess_keys is required.
Oversight in commit 70bc5833, which taught nbtree to handle array keys
during mark/restore processing, but missed this subtlety. That commit
was itself a bug fix for an issue in commit 9e8da0f7, which taught
nbtree to handle ScalarArrayOpExpr quals natively.
Author: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAH2-WzkgP3DDRJxw6DgjCxo-cu-DKrvjEv_ArkP2ctBJatDCYg@mail.gmail.com
Backpatch: 11- (all supported branches).
Branch
------
REL_15_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/cac37c1a1b7c64e60832b764e3828a9aca95bc48
Modified Files
--------------
src/backend/access/nbtree/nbtree.c | 1 +
src/backend/access/nbtree/nbtutils.c | 17 ++++++++++++++++-
src/include/access/nbtree.h | 4 +++-
3 files changed, 20 insertions(+), 2 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: pg@bowt.ie, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix btmarkpos/btrestrpos array key wraparound bug.
In-Reply-To: <E1qm0SG-006XJN-HU@gemulon.postgresql.org>
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