Re: LISTEN/NOTIFY bug: VACUUM sets frozenxid past a xid in async queue

Matheus Alcantara <matheusssilv97@gmail.com>

From: "Matheus Alcantara" <matheusssilv97@gmail.com>

To: "Arseniy Mukhin" <arseniy.mukhin.dev@gmail.com>, "Matheus Alcantara" <matheusssilv97@gmail.com>

Cc: "Masahiko Sawada" <sawada.mshk@gmail.com>, "Rishu Bagga" <rishu.postgres@gmail.com>, "Yura Sokolov" <y.sokolov@postgrespro.ru>, "Daniil Davydov" <3danissimo@gmail.com>, Álvaro Herrera <alvherre@kurilemu.de>, "Alexandra Wang" <alexandra.wang.oss@gmail.com>, "PostgreSQL Hackers" <pgsql-hackers@postgresql.org>, "Tom Lane" <tgl@sss.pgh.pa.us>, "Joel Jacobson" <joel@compiler.org>

Date: 2025-10-01T11:57:38Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Clear 'xid' in dummy async notify entries written to fill up pages
- 84f1bf4afa5e 14.21 landed
- 21a9014cf00a 15.16 landed
- 0e8eaa2181d4 16.12 landed
- d80d5f099502 17.8 landed
- 82fa6b78dba1 18.2 landed
- 0bdc777e8007 19 (unreleased) landed
Fix remaining race condition with CLOG truncation and LISTEN/NOTIFY
- c2e58c0711fe 14.21 landed
- 0c862646cf2a 15.16 landed
- 44e8c60be66c 16.12 landed
- c2682810ab7d 17.8 landed
- 7b069a1876e4 18.2 landed
- 797e9ea6e54b 19 (unreleased) landed
Fix bug where we truncated CLOG that was still needed by LISTEN/NOTIFY
- eba917d360e7 14.21 landed
- 1a469d7b5b7d 15.16 landed
- 053e1868b7ee 16.12 landed
- d02c03ddc5e3 17.8 landed
- 321ec54625fd 18.2 landed
- 8eeb4a0f7c06 19 (unreleased) landed
Escalate ERRORs during async notify processing to FATAL
- 7cb05dd2d198 14.21 landed
- b1da37de21d4 15.16 landed
- c1a5bde003b8 16.12 landed
- b821c92920f0 17.8 landed
- aab4a84bb070 18.2 landed
- 1b4699090eaf 19 (unreleased) landed
Limit the size of TID lists during parallel GIN build
- c98dffcb7c70 19 (unreleased) cited

On Sun Sep 28, 2025 at 10:17 AM -03, Arseniy Mukhin wrote:
>> I agree it would be great to have more tests for such cases. As for
>> the 'committed field' patch, I think we can add a TAP test that shows
>> that listeners postpone processing of notifications until
>> notifications were marked as 'committed=false' in case of aborted
>> transactions. I tried to write one, but have not succeeded yet. Hope
>> to finish it soon.
>
> I finally managed to write a TAP test for it, so there is a new
> version with the tap test.
>
> I also realized that we can increase test coverage in
> 002_aborted_tx_notifies.pl if notifications of the aborted transaction
> span several pages. This way we can better test
> asyncQueueRollbackNotifications(). So I changed
> 002_aborted_tx_notifies.pl TAP test a bit.
>
> And there is a small indentation change in lmgr.h that should fix this
> git am warning.
>
Thanks for the patches.

I've created a CF entry so we can get more reviews and comments:
https://commitfest.postgresql.org/patch/6095/

Let's see what other think about the approach being used to fix this
issue.

--
Matheus Alcantara