Horton

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

Peter Smith <smithpb2250@gmail.com>

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From: Peter Smith <smithpb2250@gmail.com>
To: Greg Nancarrow <gregn4422@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Ajin Cherian <itsajin@gmail.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, vignesh C <vignesh21@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-06-18T02:12:58Z
Lists: pgsql-hackers 
On Thu, Jun 17, 2021 at 6:22 PM Greg Nancarrow <gregn4422@gmail.com> wrote:
>
> On Wed, Jun 16, 2021 at 9:08 AM Peter Smith <smithpb2250@gmail.com> wrote:
> >
> >
> > Please find attached the latest patch set v86*
> >
>
> A couple of comments:
>
> (1)  I think one of my suggested changes was missed (or was that intentional?):
>
> BEFORE:
> +                The LSN of the commit prepared.
> AFTER:
> +                The LSN of the commit prepared transaction.
>

No, not missed. I already dismissed that one and wrote about it when I
posted v85 [1].

>
> (2)  In light of Tom Lane's recent changes in:
>
> fe6a20ce54cbbb6fcfe9f6675d563af836ae799a (Don't use Asserts to check
> for violations of replication protocol)
>
> there appear to be some instances of such code in these patches.

Yes, I already noted [2] there are likely to be such cases which need
to be fixed.

>
> For example, in the v86-0001 patch:
>
> +/*
> + * Handle PREPARE message.
> + */
> +static void
> +apply_handle_prepare(StringInfo s)
> +{
> + LogicalRepPreparedTxnData prepare_data;
> + char gid[GIDSIZE];
> +
> + logicalrep_read_prepare(s, &prepare_data);
> +
> + Assert(prepare_data.prepare_lsn == remote_final_lsn);
>
> The above Assert() should be changed to something like:
>
> +    if (prepare_data.prepare_lsn != remote_final_lsn)
> +        ereport(ERROR,
> +                (errcode(ERRCODE_PROTOCOL_VIOLATION),
> +                 errmsg_internal("incorrect prepare LSN %X/%X in
> prepare message (expected %X/%X)",
> +                                 LSN_FORMAT_ARGS(prepare_data.prepare_lsn),
> +                                 LSN_FORMAT_ARGS(remote_final_lsn))));
>
> Without being more familiar with this code, it's difficult for me to
> judge exactly how many of such cases are in these patches.

Thanks for the above example. I will fix this one later, after
receiving some more reviews and reports of other Assert cases just
like this one.

------
[1] https://www.postgresql.org/message-id/CAHut%2BPvOVkiVBf4P5chdVSoVs5%3Da%3DF_GtTSHHoXDb4LiOM_8Qw%40mail.gmail.com
[2] https://www.postgresql.org/message-id/CAHut%2BPvdio4%3DOE6cz5pr8VcJNcAgt5uGBPdKf-tnGEMa1mANGg%40mail.gmail.com

Kind Regards,
Peter Smith.
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