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>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, vignesh C <vignesh21@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-06-09T05:40:11Z
Lists: pgsql-hackers 
On Wed, Jun 9, 2021 at 10:34 AM Ajin Cherian <itsajin@gmail.com> wrote:
>
> On Tue, Jun 8, 2021 at 4:19 PM Peter Smith <smithpb2250@gmail.com> wrote:
>
> > > 3.
> > > @@ -432,10 +432,19 @@ CreateInitDecodingContext(const char *plugin,
> > >   MemoryContextSwitchTo(old_context);
> > >
> > >   /*
> > > - * We allow decoding of prepared transactions iff the two_phase option is
> > > - * enabled at the time of slot creation.
> > > + * We allow decoding of prepared transactions when the two_phase is
> > > + * enabled at the time of slot creation, or when the two_phase option is
> > > + * given at the streaming start.
> > >   */
> > > - ctx->twophase &= MyReplicationSlot->data.two_phase;
> > > + ctx->twophase &= (ctx->twophase_opt_given || slot->data.two_phase);
> > > +
> > > + /* Mark slot to allow two_phase decoding if not already marked */
> > > + if (ctx->twophase && !slot->data.two_phase)
> > > + {
> > > + slot->data.two_phase = true;
> > > + ReplicationSlotMarkDirty();
> > > + ReplicationSlotSave();
> > > + }
> > >
> > > Why do we need to change this during CreateInitDecodingContext which
> > > is called at create_slot time? At that time, we don't need to consider
> > > any options and there is no need to toggle slot's two_phase value.
> > >
> > >
> >
> > TODO
>
> As part of the recent changes, we do turn on two_phase at create_slot time when
> the subscription is created with (copy_data = false, two_phase = on).
> So, this code is required.
>

But in that case, won't we deal it with the value passed in
CreateReplicationSlotCmd. It should be enabled after we call
ReplicationSlotCreate.

-- 
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