Horton

Re: Replication slot stats misgivings

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: vignesh C <vignesh21@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2021-04-29T05:07:00Z
Lists: pgsql-hackers 
On Wed, Apr 28, 2021 at 7:43 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Wed, Apr 28, 2021 at 3:25 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
>
> > I am not sure if any of these alternatives are a good idea. What do
> > you think? Do you have any other ideas for this?
>
> I've been considering some ideas but don't come up with a good one
> yet. It’s just an idea and not tested but how about having
> CreateDecodingContext() register before_shmem_exit() callback with the
> decoding context to ensure that we send slot stats even on
> interruption. And FreeDecodingContext() cancels the callback.
>

Is it a good idea to send stats while exiting and rely on the same? I
think before_shmem_exit is mostly used for the cleanup purpose so not
sure if we can rely on it for this purpose. I think we can't be sure
that in all cases we will send all stats, so maybe Vignesh's patch is
sufficient to cover the cases where we avoid losing it in cases where
we would have sent a large amount of data.

-- 
With Regards,
Amit Kapila.

Commits

  1. Doc: Update logical decoding stats information.

  2. Fix tests for replication slots stats.

  3. Update replication statistics after every stream/spill.

  4. Fix the computation of slot stats for 'total_bytes'.

  5. Another try to fix the test case added by commit f5fc2f5b23.

  6. Use HTAB for replication slot statistics.

  7. Fix test case added by commit f5fc2f5b23.

  8. Add information of total data processed to replication slot stats.

  9. Use NameData datatype for slotname in stats.