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: Greg Nancarrow <gregn4422@gmail.com>
Cc: vignesh C <vignesh21@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.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>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-12-15T02:49:11Z
Lists: pgsql-hackers 
On Tue, Dec 14, 2021 at 2:35 PM Greg Nancarrow <gregn4422@gmail.com> wrote:
>
> On Tue, Dec 14, 2021 at 3:23 PM vignesh C <vignesh21@gmail.com> wrote:
> >
> > While the worker is skipping one of the skip transactions specified by
> > the user and immediately if the user specifies another skip
> > transaction while the skipping of the transaction is in progress this
> > new value will be reset by the worker while clearing the skip xid. I
> > felt once the worker has identified the skip xid and is about to skip
> > the xid, the worker can acquire a lock to prevent concurrency issues:
>
> That's a good point.
> If only the last_error_xid could be skipped, then this wouldn't be an
> issue, right?
> If a different xid to skip is specified while the worker is currently
> skipping a transaction, should that even be allowed?
>

We don't expect such usage but yes, it could happen and seems not
good. I thought we can acquire Share lock on pg_subscription during
the skip but not sure it's a good idea. It would be better if we can
find a way to allow users to specify only XID that has failed.

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