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 David Rowley <dgrowleyml@gmail.com>
	message dated "Wed, 17 Jun 2026 17:04:43 +1200"
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Date: Wed, 17 Jun 2026 18:23:00 -0400
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David Rowley <dgrowleyml@gmail.com> writes:
> I pushed the patch to add the new test after modifying it to also
> include the change in the generated_stored test, but with it commented
> out. This is the method that 83ea6c540 introduced.

The buildfarm is showing clear evidence of a bug here somewhere:

https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=3Dbushmaster&dt=3D=
2026-06-17%2021%3A53%3A38
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=3Dtaipan&dt=3D2026=
-06-17%2018%3A50%3A42
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=3Dcanebrake&dt=3D2=
026-06-17%2018%3A02%3A59

All three failures look like

diff -U3 /home/bf/bf-build/taipan/HEAD/pgsql/src/test/regress/expected/gen=
erated_virtual.out /home/bf/bf-build/taipan/HEAD/pgsql.build/src/test/regr=
ess/results/generated_virtual.out
--- /home/bf/bf-build/taipan/HEAD/pgsql/src/test/regress/expected/generate=
d_virtual.out	2026-06-17 07:00:34.298450176 +0200
+++ /home/bf/bf-build/taipan/HEAD/pgsql.build/src/test/regress/results/gen=
erated_virtual.out	2026-06-17 20:51:26.084674716 +0200
@@ -731,9 +731,9 @@
 CREATE TABLE gtest21c (a int NOT NULL, b int GENERATED ALWAYS AS (a * 2) =
VIRTUAL NOT NULL, c int NOT NULL);
 INSERT INTO gtest21c (a, c) VALUES (10, 42);
 SELECT a, b, c FROM gtest21c;
- a  | b  | c  =

-----+----+----
- 10 | 20 | 42
+ a  | b  | c =

+----+----+---
+ 10 | 20 | 0
 (1 row)
 =

 DROP TABLE gtest21c;

Speculating wildly, I'm wondering about an uninitialized variable that
happens to usually have the right value.

			regards, tom lane