Horton

Re: Skipping logical replication transactions on subscriber side

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: "David G. Johnston" <david.g.johnston@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, vignesh C <vignesh21@gmail.com>, Greg Nancarrow <gregn4422@gmail.com>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, "osumi.takamichi@fujitsu.com" <osumi.takamichi@fujitsu.com>, Alexey Lesovsky <lesovsky@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2022-01-26T04:15:51Z
Lists: pgsql-hackers 
On Wed, Jan 26, 2022 at 9:36 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Wed, Jan 26, 2022 at 12:54 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> >
> > I think it is okay to clear after the first successful application of
> > any transaction. What I was not sure was about the idea of giving
> > WARNING/ERROR if the first xact to be applied is not the same as
> > skip_xid.
>
> Do you prefer not to do anything in this case?
>

I am fine with clearing the skip_xid after the first successful
application. But note, we shouldn't do catalog access for this, we can
check if it is set in MySubscription.

> >
> > >
> > > Probably, we also need to consider the case where the tablesync worker
> > > entered an error loop and the user wants to skip the transaction? The
> > > apply worker is also running at the same time but it should not clear
> > > subskipxid. Similarly, the tablesync worker should not clear
> > > subskipxid if the apply worker wants to skip the transaction.
> > >
> >
> > I think for tablesync workers, the skip_xid set via this mechanism
> > won't work as we don't have any remote_xid for them, and neither any
> > XID is reported in the view for them.
>
> If the tablesync worker raises an error while applying changes after
> finishing the copy, it also reports the error XID.
>

Right and agreed with your assessment for the same.

-- 
With Regards,
Amit Kapila.

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