Horton

Re: Skipping logical replication transactions on subscriber side

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Greg Nancarrow <gregn4422@gmail.com>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, "osumi.takamichi@fujitsu.com" <osumi.takamichi@fujitsu.com>, Alexey Lesovsky <lesovsky@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-11-01T01:54:31Z
Lists: pgsql-hackers 
On Sat, Oct 30, 2021 at 12:21 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Fri, Oct 29, 2021 at 4:49 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Fri, Oct 29, 2021 at 10:54 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > >
> > > I'm not sure it's better to drop apply worker stats after resetting
> > > skip xid (i.g., after skipping the transaction). Since the view is a
> > > cumulative view and has last_error_time, I thought we can have the
> > > apply worker stats until the subscription gets dropped.
> > >
> >
> > Fair enough. So statistics can be removed either by vacuum or drop
> > subscription. Also, if we go by this logic then there is no harm in
> > retaining the stat entries for tablesync errors. Why have different
> > behavior for apply and tablesync workers?
> >
> > I have another question in this regard. Currently, the reset function
> > seems to be resetting only the first stat entry for a subscription.
> > But can't we have multiple stat entries for a subscription considering
> > the view's cumulative nature?
> >
>
> Don't we want these stats to be dealt in the same way as tables and
> functions as all the stats entries (subscription entries) are specific
> to a particular database? If so, I think we should write/read these
> to/from db specific stats file in the same way as we do for tables or
> functions. I think in the current patch, it will unnecessarily read
> and probably write subscription stats even when those are not
> required.

Good point! So probably we should have PgStat_StatDBEntry have the
hash table for subscription worker statistics, right?

Regards,

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

Commits

  1. Test ALIGNOF_DOUBLE==4 compatibility under ALIGNOF_DOUBLE==8.

  2. Reorder subskiplsn in pg_subscription to avoid alignment issues.

  3. Add ALTER SUBSCRIPTION ... SKIP.

  4. Optionally disable subscriptions on error.

  5. Update docs of logical replication for commit 8d74fc96db.

  6. Respect permissions within logical replication.

  7. Fix regression test failure caused by commit 8d74fc96db.

  8. Add a view to show the stats of subscription workers.

  9. Add logical change details to logical replication worker errcontext.

  10. Rename LOGICAL_REP_MSG_STREAM_END to LOGICAL_REP_MSG_STREAM_STOP.

  11. Fix typo in protocol.sgml.

  12. Remove unused argument in apply_handle_commit_internal().

  13. Fix replication of in-progress transactions in tablesync worker.

  14. Reorder pg_sequence columns to avoid alignment issue