Horton

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

Amit Kapila <amit.kapila16@gmail.com>

View thread View on postgr.es
From: Amit Kapila <amit.kapila16@gmail.com>
To: Ajin Cherian <itsajin@gmail.com>
Cc: Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-12-01T03:54:45Z
Lists: pgsql-hackers 
On Tue, Dec 1, 2020 at 7:55 AM Ajin Cherian <itsajin@gmail.com> wrote:
>
> On Tue, Dec 1, 2020 at 12:46 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
>
>
> > Sure, but you can see in your example above it got skipped due to
> > start_decoding_at not due to DecodingContextReady. So, the problem as
> > mentioned by me previously was how we distinguish those cases because
> > it can skip due to start_decoding_at during restart as well when we
> > would have already sent the prepare to the subscriber.
>
> The distinguishing factor is that at restart, the Prepare does satisfy
> DecodingContextReady (because the snapshot is consistent then).
> In both cases, the prepare is prior to start_decoding_at, but when the
> prepare is before a consistent point,
> it does not satisfy DecodingContextReady.
>

I think it won't be true when we reuse some already serialized
snapshot from some other slot. It is possible that we wouldn't have
encountered such a serialized snapshot while creating a slot but later
during replication, we might use it because by that time some other
slot has serialized the one at that point.

-- 
With Regards,
Amit Kapila.

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