Horton

Re: Logical Replication of sequences

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: vignesh C <vignesh21@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Euler Taveira <euler@eulerto.com>, Michael Paquier <michael@paquier.xyz>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Hou, Zhijie/侯 志杰 <houzj.fnst@fujitsu.com>, "Katz, Jonathan" <jkatz@amazon.com>
Date: 2024-06-13T06:42:20Z
Lists: pgsql-hackers

Commits

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  1. Doc: Add documentation for sequence synchronization.

  2. Remove unused assignment in CREATE PUBLICATION grammar.

  3. Add seq_sync_error_count to subscription statistics.

  4. Fix few issues in commit 5509055d69.

  5. Add sequence synchronization for logical replication.

  6. Add worker type argument to logical replication worker functions.

  7. Introduce "REFRESH SEQUENCES" for subscriptions.

  8. Refactor logical worker synchronization code into a separate file.

  9. Standardize use of REFRESH PUBLICATION in code and messages.

  10. Add "ALL SEQUENCES" support to publications.

  11. Expose sequence page LSN via pg_get_sequence_data.

  12. Resume conflict-relevant data retention automatically.

  13. Post-commit review fixes for 228c370868.

  14. Generate GUC tables from .dat file

On Thu, Jun 13, 2024 at 11:53 AM vignesh C <vignesh21@gmail.com> wrote:
>
> On Thu, 13 Jun 2024 at 10:27, Dilip Kumar <dilipbalaut@gmail.com> wrote:

> > Thanks for the explanation, but I am still not getting it completely,
> > do you mean to say unless all the sequences are not synced any of the
> > sequences would not be marked "ready" in pg_subscription_rel? Is that
> > necessary? I mean why we can not sync the sequences one by one and
> > mark them ready?  Why it is necessary to either have all the sequences
> > synced or none of them?
>
> Since updating the sequence is one operation and setting
> pg_subscription_rel is another, I was trying to avoid a situation
> where the sequence is updated but its state is not reflected in
> pg_subscription_rel. It seems you are suggesting that it's acceptable
> for the sequence to be updated even if its state isn't updated in
> pg_subscription_rel, and in such cases, the sequence value does not
> need to be reverted.

Right, the complexity we're adding to achieve a behavior that may not
be truly desirable is a concern. For instance, if we mark the status
as ready but do not sync the sequences, it could lead to issues.
However, if we have synced some sequences but encounter a failure
without marking the status as ready, I don't consider it inconsistent
in any way.  But anyway, now I understand your thinking behind that so
it's a good idea to leave this design behavior for a later decision.
Gathering more opinions and insights during later stages will provide
a clearer perspective on how to proceed with this aspect.  Thanks.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com