Re: Replication slot stats misgivings

From: vignesh C <vignesh21(at)gmail(dot)com>
To: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
Subject: Re: Replication slot stats misgivings
Date: 2021-04-12 16:09:14
Message-ID: CALDaNm04ifghONx-=qOGAphqHMG1wg1teKgxrAi_tSMO5fWiJg@mail.gmail.com
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On Mon, Apr 12, 2021 at 7:03 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Mon, Apr 12, 2021 at 9:36 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Mon, Apr 12, 2021 at 5:29 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > >
> > > On Mon, Apr 12, 2021 at 8:08 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > >
> > > > On Mon, Apr 12, 2021 at 4:34 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > > > >
> > > > > On Mon, Apr 12, 2021 at 6:19 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > > > >
> > > > > > On Mon, Apr 12, 2021 at 10:27 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > > > > > >
> > > > > > > On Sat, Apr 10, 2021 at 9:53 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > > > > > >
> > > > > > > >
> > > > > > > > It seems Vignesh has changed patches based on the latest set of
> > > > > > > > comments so you might want to rebase.
> > > > > > >
> > > > > > > I've merged my patch into the v6 patch set Vignesh submitted.
> > > > > > >
> > > > > > > I've attached the updated version of the patches. I didn't change
> > > > > > > anything in the patch that changes char[NAMEDATALEN] to NameData (0001
> > > > > > > patch) and patches that add tests.
> > > > > > >
> > > > > >
> > > > > > I think we can push 0001. What do you think?
> > > > >
> > > > > +1
> > > > >
> > > > > >
> > > > > > > In 0003 patch I reordered the
> > > > > > > output parameters of pg_stat_replication_slots; showing total number
> > > > > > > of transactions and total bytes followed by statistics for spilled and
> > > > > > > streamed transactions seems appropriate to me.
> > > > > > >
> > > > > >
> > > > > > I am not sure about this because I think we might want to add some
> > > > > > info of stream/spill bytes in total_bytes description (something like
> > > > > > stream/spill bytes are not in addition to total_bytes).
> > >
> > > BTW doesn't it confuse users that stream/spill bytes are not in
> > > addition to total_bytes? User will need to do "total_bytes +
> > > spill/stream_bytes" to know the actual total amount of data sent to
> > > the decoding output plugin, is that right?
> > >
> >
> > No, total_bytes includes the spill/stream bytes. So, the user doesn't
> > need to do any calculation to compute totel_bytes sent to output
> > plugin.
>
> The following test for the latest v8 patch seems to show different.
> total_bytes is 1808 whereas spill_bytes is 13200000. Am I missing
> something?

I will check this issue and post my analysis.

Regards,
Vignesh

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