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: Peter Smith <smithpb2250@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, vignesh C <vignesh21@gmail.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, Ajin Cherian <itsajin@gmail.com>, Greg Nancarrow <gregn4422@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-07-19T06:41:35Z
Lists: pgsql-hackers 
On Mon, Jul 19, 2021 at 9:19 AM Peter Smith <smithpb2250@gmail.com> wrote:
>
> On Mon, Jul 19, 2021 at 12:43 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Mon, Jul 19, 2021 at 1:55 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > >
> > > Amit Kapila <amit.kapila16@gmail.com> writes:
> > > > Pushed.
> > >
> > > I think you'd be way better off making the gid fields be "char *"
> > > and pstrdup'ing the result of pq_getmsgstring.  Another possibility
> > > perhaps is to use strlcpy, but I'd only go that way if it's important
> > > to constrain the received strings to 200 bytes.
> > >
> >
> > I think it is important to constrain length to 200 bytes for this case
> > as here we receive a prepared transaction identifier which according
> > to docs [1] has a max length of 200 bytes. Also, in
> > ParseCommitRecord() and ParseAbortRecord(), we are using strlcpy with
> > 200 as max length to copy prepare transaction identifier. So, I think
> > it is better to use strlcpy here unless you or Peter feels otherwise.
> >
>
> OK. I have implemented this reported [1] potential buffer overrun
> using the constraining strlcpy, because the GID limitation of 200
> bytes is already mentioned in the documentation [2].
>

This will work but I think it is better to use sizeof gid buffer as we
are using in ParseCommitRecord() and ParseAbortRecord(). Tomorrow, if
due to some unforeseen reason if we change the size of gid buffer to
be different than the GIDSIZE then it will work seamlessly.

-- 
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