Horton

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

Amit Kapila <amit.kapila16@gmail.com>

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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: 2021-03-19T14:35:08Z
Lists: pgsql-hackers

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On Fri, Mar 19, 2021 at 5:03 AM Ajin Cherian <itsajin@gmail.com> wrote:
>
> Missed the patch - 0001, resending.
>

I have made miscellaneous changes in the patch which includes
improving comments, error messages, and miscellaneous coding
improvements. The most notable one is that we don't need an additional
parameter in walrcv_startstreaming, if the two_phase option is set
properly. My changes are in v63-0002-Misc-changes-by-Amit, if you are
fine with those, then please merge them in the next version. I have
omitted the dev-logs patch but feel free to submit it. I have one
question:
@@ -538,10 +550,21 @@ CreateDecodingContext(XLogRecPtr start_lsn,
..
+ /* Set two_phase_at LSN only if it hasn't already been set. */
+ if (ctx->twophase && !MyReplicationSlot->data.two_phase_at)
+ {
+ MyReplicationSlot->data.two_phase_at = start_lsn;
+ slot->data.two_phase = true;
+ ReplicationSlotMarkDirty();
+ ReplicationSlotSave();
+ SnapBuildSetTwoPhaseAt(ctx->snapshot_builder, start_lsn);
+ }

What if the walsender or apply worker restarts after setting
two_phase_at/two_phase here and updating the two_phase state in
pg_subscription? Won't we need to set SnapBuildSetTwoPhaseAt after
restart as well? If so, we probably need a else if (ctx->twophase)
{Assert (slot->data.two_phase_at);
SnapBuildSetTwoPhaseAt(ctx->snapshot_builder,
slot->data.two_phase_at);}. Am, I missing something?

-- 
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