| From: | "Joel Jacobson" <joel(at)compiler(dot)org> |
|---|---|
| To: | Álvaro Herrera <alvherre(at)kurilemu(dot)de>, "Arseniy Mukhin" <arseniy(dot)mukhin(dot)dev(at)gmail(dot)com> |
| Cc: | "Matheus Alcantara" <matheusssilv97(at)gmail(dot)com>, "Masahiko Sawada" <sawada(dot)mshk(at)gmail(dot)com>, "Rishu Bagga" <rishu(dot)postgres(at)gmail(dot)com>, "Yura Sokolov" <y(dot)sokolov(at)postgrespro(dot)ru>, "Daniil Davydov" <3danissimo(at)gmail(dot)com>, "Alexandra Wang" <alexandra(dot)wang(dot)oss(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: LISTEN/NOTIFY bug: VACUUM sets frozenxid past a xid in async queue |
| Date: | 2025-10-19 17:14:07 |
| Message-ID: | 25651193-da4e-4185-a564-f2efa6b0c8a4@app.fastmail.com |
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| Lists: | pgsql-hackers |
On Fri, Oct 17, 2025, at 15:51, Álvaro Herrera wrote:
> I have the impression that this thread has lost focus on the idea of
> producing a backpatchable bugfix. The last proposed patch has a lot of
> new mechanism that doesn't seem suitable for backpatch. I could be
> wrong of course.
I've tried to create a minimal isolated fix, hopefully suitable for
backpatching, with no new mechanisms, other than the added
GetOldestQueuedNotifyXid used by vac_update_datfrozenxid.
It's based on the approach discussed earlier in this thread, that just
goes through the notification queue from QUEUE_TAIL to QUEUE_HEAD, to
find the oldestXid in the current database.
Implementation:
* Break out SLRU read page code from asyncQueueReadAllNotifications into
new helper-function asyncQueueReadPageToBuffer.
* Add GetOldestQueuedNotifyXid which uses the new helper-function
asyncQueueReadPageToBuffer.
It passes the 001_xid_freeze.pl test, not included in this patch.
/Joel
| Attachment | Content-Type | Size |
|---|---|---|
| fix_notify_datfrozenxid.txt | text/plain | 7.5 KB |
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