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  1. Add wait event for the group commit delay before WAL flush

  1. Add wait event for CommitDelay

    Rafia Sabih <rafia.pghackers@gmail.com> — 2025-12-05T10:10:34Z

    Hello there,

So, my colleague Ants Aasma found that a wait_event is missing for
CommitDelay. This just looks like it was missed, please enlighten if it is
left out intentionally.
For now, I worked on this patch to add it.

-- 
Regards,
Rafia Sabih
CYBERTEC PostgreSQL International GmbH

  2. Re: Add wait event for CommitDelay

    Sami Imseih <samimseih@gmail.com> — 2025-12-05T16:15:19Z

    Hi,

> So, my colleague Ants Aasma found that a wait_event is missing for CommitDelay.
> This just looks like it was missed, please enlighten if it is left out intentionally.

I do not know if it was left out intentionally, there are no comments on that
matter.

I am not sure how widely used this GUC is, but from the quick test that I
did using pgench TPC-B workload with 50 clients, it seems useful
since a DBA can set commit_delay too high and you will easily observe
a single backend constantly in this delay which will impact tps.
It's good to show this clearly as a wait event.

As far as the patch goes, It makes sense to put this under "WaitEventTimeout",
but it should be placed after CHECKPOINT_WRITE_DELAY in
alphabetical order, and the description could be improved a bit.
How about? "Waiting for the commit delay before WAL flush."

--
Sami Imseih
Amazon Web Services (AWS)

  3. Re: Add wait event for CommitDelay

    Michael Paquier <michael@paquier.xyz> — 2025-12-05T22:19:24Z

    On Fri, Dec 05, 2025 at 10:15:19AM -0600, Sami Imseih wrote:
> I am not sure how widely used this GUC is, but from the quick test that I
> did using pgench TPC-B workload with 50 clients, it seems useful
> since a DBA can set commit_delay too high and you will easily observe
> a single backend constantly in this delay which will impact tps.
> It's good to show this clearly as a wait event.

I have never used it myself, but I can see why it could be useful for
monitoring here.  No objections to this addition here. 

> As far as the patch goes, It makes sense to put this under "WaitEventTimeout",
> but it should be placed after CHECKPOINT_WRITE_DELAY in
> alphabetical order, and the description could be improved a bit.
> How about? "Waiting for the commit delay before WAL flush."

Yes, your description is more useful than what the patch is proposing.
--
Michael

  4. Re: Add wait event for CommitDelay

    Rafia Sabih <rafia.pghackers@gmail.com> — 2025-12-08T15:20:46Z

    On Fri, 5 Dec 2025 at 17:15, Sami Imseih <samimseih@gmail.com> wrote:

> Hi,
>
> > So, my colleague Ants Aasma found that a wait_event is missing for
> CommitDelay.
> > This just looks like it was missed, please enlighten if it is left out
> intentionally.
>
> I do not know if it was left out intentionally, there are no comments on
> that
> matter.
>
> I am not sure how widely used this GUC is, but from the quick test that I
> did using pgench TPC-B workload with 50 clients, it seems useful
> since a DBA can set commit_delay too high and you will easily observe
> a single backend constantly in this delay which will impact tps.
> It's good to show this clearly as a wait event.
>
> As far as the patch goes, It makes sense to put this under
> "WaitEventTimeout",
> but it should be placed after CHECKPOINT_WRITE_DELAY in
> alphabetical order, and the description could be improved a bit.
> How about? "Waiting for the commit delay before WAL flush."
>
> Thanks for the review of the patch. Please find the attachment for the
updated version.

-- 
Regards,
Rafia Sabih
CYBERTEC PostgreSQL International GmbH

  5. Re: Add wait event for CommitDelay

    Sami Imseih <samimseih@gmail.com> — 2025-12-08T19:16:28Z

    > Thanks for the review of the patch. Please find the attachment for the updated version.

Thanks! v2 LGTM

--
Sami Imseih
Amazon Web Services (AWS)

  6. Re: Add wait event for CommitDelay

    Heikki Linnakangas <hlinnaka@iki.fi> — 2025-12-09T15:23:11Z

    On 08/12/2025 21:16, Sami Imseih wrote:
>> Thanks for the review of the patch. Please find the attachment for the updated version.
> 
> Thanks! v2 LGTM

Committed, thanks!

- Heikki