From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <dgrowleyml@gmail.com>
cc: Chao Li <li.evan.chao@gmail.com>, Peter Eisentraut <peter@eisentraut.org>,
        Andres Freund <andres@anarazel.de>,
        Postgres hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Fix tuple deformation with virtual generated NOT NULL columns
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Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Wed, 17 Jun 2026 18:23:00 -0400"
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Date: Wed, 17 Jun 2026 18:45:49 -0400
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I wrote:
> Speculating wildly, I'm wondering about an uninitialized variable that
> happens to usually have the right value.

Nope: valgrind finds nothing, and neither does debug_discard_caches.
What does reproduce it, with seeming 100% reliability, is

set jit =3D 1;
set jit_above_cost =3D 0;
set jit_optimize_above_cost =3D 1000;
CREATE TABLE gtest21c (a int NOT NULL, b int GENERATED ALWAYS AS (a * 2) V=
IRTUAL NOT NULL, c int NOT NULL);
INSERT INTO gtest21c (a, c) VALUES (10, 42);
table gtest21c;

I conclude that something in the JIT code for tuple formation
is unaware of virtual generated columns.

			regards, tom lane