Horton

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

Ajin Cherian <itsajin@gmail.com>

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From: Ajin Cherian <itsajin@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-12-08T08:31:15Z
Lists: pgsql-hackers

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On Tue, Dec 1, 2020 at 6:26 PM Amit Kapila <amit.kapila16@gmail.com> wrote:

> To skip it, we need to send GID in begin message and then on
> subscriber-side, check if the prepared xact already exists, if so then
> set a flag. The flag needs to be set in begin/start_stream and reset
> in stop_stream/commit/abort. Using the flag, we can skip the entire
> contents of the prepared xact. In ReorderFuffer-side also, we need to
> get and set GID in txn even when we skip it because we need to send
> the same at commit time. In this solution, we won't be able to send it
> during normal start_stream because by that time we won't know GID and
> I think that won't be required. Note that this is only required when
> we skipped sending prepare, otherwise, we just need to send
> Commit-Prepared at commit time.

I have implemented these changes and tested the fix using the test
setup I had shared above and it seems to be working fine.
I have also tested restarts that simulate duplicate prepares being
sent by the publisher and verified that it is handled correctly by the
subscriber.
Do have a look at the changes and let me know if you have any comments.

regards,
Ajin Cherian
Fujitsu Australia

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