| From: | Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru> |
|---|---|
| To: | Matheus Alcantara <matheusssilv97(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Cc: | Daniil Davydov <3danissimo(at)gmail(dot)com>, Álvaro Herrera <alvherre(at)kurilemu(dot)de>, Alexandra Wang <alexandra(dot)wang(dot)oss(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: LISTEN/NOTIFY bug: VACUUM sets frozenxid past a xid in async queue |
| Date: | 2025-09-02 07:37:59 |
| Message-ID: | d186fba0-dc65-4274-aa96-3906bbb2e530@postgrespro.ru |
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| Lists: | pgsql-hackers |
29.08.2025 01:31, Matheus Alcantara пишет:
> On Thu Aug 21, 2025 at 8:14 PM -03, Matheus Alcantara wrote:
>> I'll work on this considering the initial Daniil comments at [1]
>>
>> [1] https://www.postgresql.org/message-id/CAJDiXgg1ArRB1-6wLtXfVVnQ38P9Y%2BCDfEc9M2TXiOf_4kfBMg%40mail.gmail.com
>>
> I've been working on this on the last few days, please see the attached
> patch version.
>
> In this new version I tried to follow the suggestion from Daniil of
> scanning all pages from tail to head of the async queue.
Since we still need to scan those pages, couldn't we mark finished
transactions as committed/aborted?
This way we may to not hold datfrozenxid for a long time and will allow
both safe clog truncation and safe async queue notification.
More over, most notifications could be marked as completed in
AtCommit_Notify already. So there is a need to recheck a few notifications
that were written but not marked in AtCommit_Notify.
Since AsyncQueueEntry field is used only to check visibility, looks like it
is safe to set it to FrozenTransactionId.
--
regards
Yura Sokolov aka funny-falcon
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