Re: Replication slot stats misgivings

On Sun, Apr 18, 2021 at 12:13 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Sun, Apr 18, 2021 at 7:36 AM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> >
> > On Sun, Apr 18, 2021 at 3:51 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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/