Re: Replication slot stats misgivings

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? The doc says "Amount of
decoded transactions data sent to the decoding output plugin while
decoding the changes from WAL for this slot" but I think we also send
decoded data that had been spilled to the decoding output plugin.

> >
> > Okay.
> >
> > > So probably
> > > keeping these new counters at the end makes more sense to me.
> >
> > But I think all of those counters are new for users since
> > pg_stat_replication_slots view will be introduced to PG14, no?
> >
>
> Right, I was referring to total_txns and total_bytes attributes. I
> think keeping them at end after spill and stream counters should be
> okay.

Okay, understood.

Regards,

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