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: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Alexey Lesovsky <lesovsky@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-07-20T09:27:31Z
Lists: pgsql-hackers 
On Tue, Jul 20, 2021 at 6:56 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Mon, Jul 19, 2021 at 8:38 PM houzj.fnst@fujitsu.com
> <houzj.fnst@fujitsu.com> wrote:
> >
> > 3) For 0003 patch, if user set skip_xid to a wrong xid which have not been
> >    assigned, and then will the change be skipped when the xid is assigned in
> >    the future even if it doesn't cause any conflicts ?
>
> Yes. Currently, setting a correct xid is the user's responsibility. I
> think it would be better to disable it or emit WARNING/ERROR when the
> user mistakenly set the wrong xid if we find out a convenient way to
> detect that.
>

I think in this regard we should clearly document how this can be
misused by users. I see that you have mentioned about skip_xid but
maybe we can add more on how it could lead to skipping a
non-conflicting XID and can lead to an inconsistent replica. As
discussed earlier as well, users can anyway do similar harm by using
pg_replication_slot_advance(). I think if possible we might want to
give some examples as well where it would be helpful for users to use
this functionality.

-- 
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