Re: Optimize LISTEN/NOTIFY

Joel Jacobson <joel@compiler.org>

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From: "Joel Jacobson" <joel@compiler.org>

To: "Arseniy Mukhin" <arseniy.mukhin.dev@gmail.com>

Cc: pgsql-hackers <pgsql-hackers@postgresql.org>

Date: 2025-11-13T07:13:28Z

Lists: pgsql-hackers

Attachments

0001-optimize_listen_notify-v27.patch (application/octet-stream)
0002-optimize_listen_notify-v27.patch (application/octet-stream)

On Thu, Nov 13, 2025, at 07:36, Arseniy Mukhin wrote:
> On Thu, Nov 13, 2025 at 9:28 AM Joel Jacobson <joel@compiler.org> wrote:
>> I think this confirms that listeners can actually stop somewhere in between
>> queueHeadBeforeWrite and queueHeadAfterWrite.
>
>
> Ahh, yes, I think you are right. I missed that notifiers update the
> head when they move to the next page. Thank you for the detailed
> example and sorry for taking your time with it. I agree that
> QUEUE_POS_PRECEDES(pos, queueHeadAfterWrite) is correct and covers
> more cases where we can do direct advancement.

Thanks for investigating this; we now both have an even stronger mental
model of the code.

Attached, please find a new version rebased on top of the bug fix
patches that just got committed in 0bdc777, 797e9ea, 8eeb4a0, and
1b46990.

/Joel