Horton

Re: [HACKERS] logical decoding of two-phase transactions

vignesh C <vignesh21@gmail.com>

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From: vignesh C <vignesh21@gmail.com>
To: Peter Smith <smithpb2250@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-03-09T04:21:50Z
Lists: pgsql-hackers 
On Tue, Mar 9, 2021 at 9:14 AM Peter Smith <smithpb2250@gmail.com> wrote:
>
> On Mon, Mar 8, 2021 at 4:58 PM vignesh C <vignesh21@gmail.com> wrote:
> >
> >         LOGICAL_REP_MSG_TYPE = 'Y',
> > +       LOGICAL_REP_MSG_BEGIN_PREPARE = 'b',
> > +       LOGICAL_REP_MSG_PREPARE = 'P',
> > +       LOGICAL_REP_MSG_COMMIT_PREPARED = 'K',
> > +       LOGICAL_REP_MSG_ROLLBACK_PREPARED = 'r',
> >         LOGICAL_REP_MSG_STREAM_START = 'S',
> >         LOGICAL_REP_MSG_STREAM_END = 'E',
> >         LOGICAL_REP_MSG_STREAM_COMMIT = 'c',
> > -       LOGICAL_REP_MSG_STREAM_ABORT = 'A'
> > +       LOGICAL_REP_MSG_STREAM_ABORT = 'A',
> > +       LOGICAL_REP_MSG_STREAM_PREPARE = 'p'
> >  } LogicalRepMsgType;
> > As we start adding more and more features, we will have to start
> > adding more message types, using meaningful characters might become
> > difficult. Should we start using numeric instead for the new feature
> > getting added?
>
> This may or may not become a problem sometime in the future, but I
> think the feedback is not really specific to the current patch set so
> I am skipping it at this time.
>
> If you want, maybe create it as a separate thread, Is it OK?

I was thinking of changing the newly added message types to something
like below:
>         LOGICAL_REP_MSG_TYPE = 'Y',
> +       LOGICAL_REP_MSG_BEGIN_PREPARE = 1,
> +       LOGICAL_REP_MSG_PREPARE = 2,
> +       LOGICAL_REP_MSG_COMMIT_PREPARED = 3,
> +       LOGICAL_REP_MSG_ROLLBACK_PREPARED = 4,
>         LOGICAL_REP_MSG_STREAM_START = 'S',
>         LOGICAL_REP_MSG_STREAM_END = 'E',
>         LOGICAL_REP_MSG_STREAM_COMMIT = 'c',
> -       LOGICAL_REP_MSG_STREAM_ABORT = 'A'
> +       LOGICAL_REP_MSG_STREAM_ABORT = 'A',
> +       LOGICAL_REP_MSG_STREAM_PREPARE = 5
>  } LogicalRepMsgType;

Changing these values at a later time may become difficult as it can
break backward compatibility. But if you feel the existing values are
better we can keep it as it is and think of it later when we add more
message types.

Regards,
Vignesh

Commits

  1. Add prepare API support for streaming transactions in logical replication.

  2. Doc: minor improvements for logical replication protocol documentation.

  3. Fix test failure in 021_twophase.pl.

  4. Refactor to make common functions in proto.c and worker.c.

  5. Unify PostgresNode's new() and get_new_node() methods

  6. Fix potential buffer overruns in proto.c.

  7. Add support for prepared transactions to built-in logical replication.

  8. Refactor function parse_subscription_options.

  9. Allow enabling two-phase option via replication protocol.

  10. Don't use Asserts to check for violations of replication protocol.

  11. Improve psql tab completion for options of subcriptions and publications

  12. Rearrange logrep worker's snapshot handling some more.

  13. doc: Update information of new messages for logical replication.

  14. ALTER SUBSCRIPTION ... ADD/DROP PUBLICATION

  15. Allow pgoutput to send logical decoding messages.

  16. Refactor function parse_output_parameters.

  17. Avoid repeated decoding of prepared transactions after a restart.

  18. Fix an oversight in ReorderBufferFinishPrepared.

  19. Allow multiple xacts during table sync in logical replication.

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

  21. Fix 'skip-empty-xacts' option in test_decoding for streaming mode.

  22. Use Enum for top level logical replication message types.

  23. Add support for streaming to built-in logical replication.

  24. Fix the logical streaming test.

  25. Implement streaming mode in ReorderBuffer.

  26. Extend the logical decoding output plugin API with stream methods.

  27. Store 2PC GID in commit/abort WAL recs for logical decoding