From: David Rowley <drowley@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix incorrect zero extension of Datum in JIT tuple deform code
Date: Thu, 23 Oct 2025 00:13:33 +0000
Message-ID: <E1vBixR-0032DD-2w@gemulon.postgresql.org> (raw)
Fix incorrect zero extension of Datum in JIT tuple deform code
When JIT deformed tuples (controlled via the jit_tuple_deforming GUC),
types narrower than sizeof(Datum) would be zero-extended up to Datum
width. This wasn't the same as what fetch_att() does in the standard
tuple deforming code. Logically the values are the same when fetching
via the DatumGet*() marcos, but negative numbers are not the same in
binary form.
In the report, the problem was manifesting itself with:
ERROR: could not find memoization table entry
in a query which had a "Cache Mode: binary" Memoize node. However, it's
currently unclear what else is affected. Anything that uses
datum_image_eq() or datum_image_hash() on a Datum from a tuple deformed by
JIT could be affected, but it may not be limited to that.
The fix for this is simple: use signed extension instead of zero
extension.
Many thanks to Emmanuel Touzery for reporting this issue and providing
steps and backup which allowed the problem to easily be recreated.
Reported-by: Emmanuel Touzery <emmanuel.touzery@plandela.si>
Author: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/DB8P194MB08532256D5BAF894F241C06393F3A@DB8P194MB0853.EURP194.PROD.OUTLOOK.COM
Backpatch-through: 13
Branch
------
REL_16_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/3398b0d027852ff1ef4a3be28612a5731f6e52f3
Modified Files
--------------
src/backend/jit/llvm/llvmjit_deform.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-committers@postgresql.org
Cc: drowley@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix incorrect zero extension of Datum in JIT tuple deform code
In-Reply-To: <E1vBixR-0032DD-2w@gemulon.postgresql.org>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox