MIME-Version: 1.0
From: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Date: Sun, 12 Apr 2026 18:59:28 -0700
Message-ID: 
 <CAHg+QDexGTmCZzx=73gXkY2ZADS6LRhpnU+-8Y_QmrdTS6yUhA@mail.gmail.com>
Subject: Bug: Rule actions see wrong values for generated columns (NEW.gen
 reads OLD value)
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Content-Type: multipart/alternative; boundary="000000000000f23f87064f4dd59b"
Archived-At: 
 <https://www.postgresql.org/message-id/CAHg%2BQDexGTmCZzx%3D73gXkY2ZADS6LRhpnU%2B-8Y_QmrdTS6yUhA%40mail.gmail.com>
Precedence: bulk

--000000000000f23f87064f4dd59b
Content-Type: text/plain; charset="UTF-8"

Hi hackers,

NEW.<generated_coulmn> is resolved to the OLD row's value
for update or NULL for insert cases in a DO ALSO rule action for
generated columns.  This bug affects both stored and virtual
generated columns. Reporting here to see if this is a known issue
with generated columns.

Repro:

CREATE TABLE t (id int PRIMARY KEY, a int,
                gen int GENERATED ALWAYS AS (a * 2) VIRTUAL);
CREATE TABLE t_log (op text, old_gen int, new_gen int);

CREATE RULE t_log AS ON UPDATE TO t
  DO ALSO INSERT INTO t_log VALUES ('UPD', OLD.gen, NEW.gen);

INSERT INTO t (id, a) VALUES (1, 5);
UPDATE t SET a = 100 WHERE id = 1;

postgres=# SELECT * FROM t;
 id |  a  | gen
----+-----+-----
  1 | 100 | 200
(1 row)

postgres=# SELECT * FROM t_log;
 op  | old_gen | new_gen
-----+---------+---------
 UPD |      10 |      10
(1 row)

Thanks,
Satya

--000000000000f23f87064f4dd59b
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">Hi hackers,<br><br>NEW.&lt;generated_coulmn&gt; is resolve=
d to the OLD row&#39;s value<div>for update or NULL for insert cases in a D=
O ALSO rule action for</div><div>generated columns.=C2=A0 This bug affects =
both stored and virtual=C2=A0</div><div>generated columns. Reporting here t=
o see if this is a known issue<br></div><div>with generated columns.</div><=
div><br></div><div>Repro:</div><div><br></div><div>CREATE TABLE t (id int P=
RIMARY KEY, a int,<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 gen int GENERATED ALWAYS AS (a * 2) VIRTUAL);<br>CREATE TABLE t_log (op=
 text, old_gen int, new_gen int);<br><br>CREATE RULE t_log AS ON UPDATE TO =
t<br>=C2=A0 DO ALSO INSERT INTO t_log VALUES (&#39;UPD&#39;, OLD.gen, NEW.g=
en);<br><br>INSERT INTO t (id, a) VALUES (1, 5);=C2=A0<br>UPDATE t SET a =
=3D 100 WHERE id =3D 1;=C2=A0</div><div><br></div><div>postgres=3D# SELECT =
* FROM t;<br>=C2=A0id | =C2=A0a =C2=A0| gen <br>----+-----+-----<br>=C2=A0 =
1 | 100 | 200<br>(1 row)<br><br>postgres=3D# SELECT * FROM t_log;<br>=C2=A0=
op =C2=A0| old_gen | new_gen <br>-----+---------+---------<br>=C2=A0UPD | =
=C2=A0 =C2=A0 =C2=A010 | =C2=A0 =C2=A0 =C2=A010<br>(1 row)</div><div><br></=
div><div>Thanks,</div><div>Satya</div></div>

--000000000000f23f87064f4dd59b--