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: 2020-11-24T09:58:57Z
Lists: pgsql-hackers 
On Mon, Nov 23, 2020 at 10:35 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> For the first two, as the xact is still not visible to others so we
> don't need to make it behave like a committed txn. To make the (DDL)
> changes visible to the current txn, the message
> REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID copies the snapshot which
> fills the subxip array. This will be sufficient to make the changes
> visible to the current txn. For the third, I have checked the code
> that whenever we have any change message the base snapshot gets set
> via SnapBuildProcessChange. It is possible that I have missed
> something but I don't want to call SnapbuildCommittedTxn in
> DecodePrepare unless we have a clear reason for the same so leaving it
> for now. Can you or someone see any reason for the same?

I reviewed and tested this and like you said, SnapBuildProcessChange
sets the base snapshot for every change.
I did various tests using DDL updates and haven't seen any issues so
far. I agree with your analysis.

regards,
Ajin

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