Re: Failed transaction statistics to measure the logical replication progress

On Mon, Dec 13, 2021 at 5:48 PM osumi(dot)takamichi(at)fujitsu(dot)com
<osumi(dot)takamichi(at)fujitsu(dot)com> wrote:
>
> On Monday, December 13, 2021 6:19 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > On Tue, Dec 7, 2021 at 3:12 PM osumi(dot)takamichi(at)fujitsu(dot)com
> > <osumi(dot)takamichi(at)fujitsu(dot)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?

--
With Regards,
Amit Kapila.