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In-Reply-To: 
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From: vignesh C <vignesh21@gmail.com>
Date: Wed, 15 Dec 2021 18:21:44 +0530
Message-ID: 
 <CALDaNm0Wg8XwfqUVnBSSahOtNxGDLNOW1_tc4ikZK=tGfqje-A@mail.gmail.com>
Subject: Re: Failed transaction statistics to measure the logical replication
 progress
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "osumi.takamichi@fujitsu.com" <osumi.takamichi@fujitsu.com>,
 Masahiko Sawada <sawada.mshk@gmail.com>,
	Greg Nancarrow <gregn4422@gmail.com>,
 "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>,
	"pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
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 <https://www.postgresql.org/message-id/CALDaNm0Wg8XwfqUVnBSSahOtNxGDLNOW1_tc4ikZK%3DtGfqje-A%40mail.gmail.com>
Precedence: bulk

On Tue, Dec 14, 2021 at 7:58 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Mon, Dec 13, 2021 at 5:48 PM osumi.takamichi@fujitsu.com
> <osumi.takamichi@fujitsu.com> wrote:
> >
> > On Monday, December 13, 2021 6:19 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > > On Tue, Dec 7, 2021 at 3:12 PM osumi.takamichi@fujitsu.com
> > > <osumi.takamichi@fujitsu.com> wrote:
> > >
> > > Few questions and comments:
> > Thank you for your comments !
> >
> > > ========================
> > > 1.
> > > The <structname>pg_stat_subscription_workers</structname> view will
> > > contain
> > >     one row per subscription worker on which errors have occurred, for workers
> > >     applying logical replication changes and workers handling the initial data
> > > -   copy of the subscribed tables.  The statistics entry is removed when the
> > > -   corresponding subscription is dropped.
> > > +   copy of the subscribed tables. Also, the row corresponding to the apply
> > > +   worker shows all transaction statistics of both types of workers on the
> > > +   subscription. The statistics entry is removed when the corresponding
> > > +   subscription is dropped.
> > >
> > > Why did you choose to show stats for both types of workers in one row?
> > This is because if we have hundreds or thousands of tables for table sync,
> > we need to create many entries to cover them and store the entries for all tables.
> >
>
> If we fear a large number of entries for such workers then won't it be
> better to show the value of these stats only for apply workers. I
> think normally the table sync workers perform only copy operation or
> maybe a fixed number of xacts, so, one might not be interested in the
> transaction stats of these workers. I find merging only specific stats
> of two different types of workers confusing.
>
> What do others think about this?

We can remove the table sync workers transaction stats count to avoid
confusion, take care of the documentation changes too accordingly.

Regards,
Vignesh