Horton

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

Greg Nancarrow <gregn4422@gmail.com>

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From: Greg Nancarrow <gregn4422@gmail.com>
To: Peter Smith <smithpb2250@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: 2021-06-17T08:22:24Z
Lists: pgsql-hackers 
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.


(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.

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.

Regards,
Greg Nancarrow
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