Horton

Re: Replication slot stats misgivings

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: vignesh C <vignesh21@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2021-04-18T13:21:16Z
Lists: pgsql-hackers

Attachments

On Sun, Apr 18, 2021 at 12:13 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Sun, Apr 18, 2021 at 7:36 AM vignesh C <vignesh21@gmail.com> wrote:
> >
> > On Sun, Apr 18, 2021 at 3:51 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > >
> > > I wrote:
> > > > The buildfarm suggests that this isn't entirely stable:
> > > > https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=anole&dt=2021-04-17%2011%3A14%3A49
> > > > https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=bichir&dt=2021-04-17%2016%3A30%3A15
> > >
> > > Oh, I missed that hyrax is showing the identical symptom:
> > >
> > > https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=hyrax&dt=2021-04-16%2007%3A05%3A44
> > >
> > > So you might try CLOBBER_CACHE_ALWAYS to see if you can reproduce it
> > > that way.
> > >
> >
> > I will try to check and identify why it is failing.
> >
>
> I think the failure is due to the reason that in the new tests after
> reset, we are not waiting for the stats message to be delivered as we
> were doing in other cases. Also, for the new test (non-spilled case),
> we need to decode changes as we are doing for other tests, otherwise,
> it will show the old stats.
>

Yes, also the following expectation in expected/stats.out is wrong:

SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS
spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS
total_bytes FROM pg_stat_replication_slots;
    slot_name    | spill_txns | spill_count | total_txns | total_bytes
-----------------+------------+-------------+------------+-------------
 regression_slot | f          | f           | t          | t
(1 row)

We should expect all values are 0. Please find attached the patch.

Regards,

-- 
Masahiko Sawada
EDB:  https://www.enterprisedb.com/

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.