Horton

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

vignesh C <vignesh21@gmail.com>

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From: vignesh C <vignesh21@gmail.com>
To: Ajin Cherian <itsajin@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-03-16T10:36:03Z
Lists: pgsql-hackers 
On Mon, Mar 15, 2021 at 6:14 PM Ajin Cherian <itsajin@gmail.com> wrote:
>
> On Mon, Mar 15, 2021 at 2:04 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>>
>> I think something on these lines should be much
>> easier than the spool-file implementation unless we see any problem
>> with this idea.
>>
>
> Here's a new patch-set that implements this new solution proposed by Amit.

Thanks for the updated patch.
Few comments:
1) These are no longer needed as it has been removed with the new changes.
@@ -1959,6 +1962,8 @@ ProtocolVersion
 PrsStorage
 PruneState
 PruneStepResult
+PsfFile
+PsfHashEntry

2) "Binary mode and streaming and two_phase" should be "Binary mode,
streaming and two_phase" in the below code:
@@ -6097,13 +6097,15 @@ describeSubscriptions(const char *pattern, bool verbose)

        if (verbose)
        {
-               /* Binary mode and streaming are only supported in v14
and higher */
+               /* Binary mode and streaming and two_phase are only
supported in v14 and higher */
                if (pset.sversion >= 140000)
                        appendPQExpBuffer(&buf,

3) We have some reference to psf spoolfile, this should be removed.
Also check if the assert should be <= or ==.
+       /*
+        * Normally, prepare_lsn == remote_final_lsn, but if this
prepare message
+        * was dispatched via the psf spoolfile replay then the remote_final_lsn
+        * is set to commit lsn instead. Hence the <= instead of == check below.
+        */
+       Assert(prepare_data.prepare_lsn <= remote_final_lsn);

4) Similarly in below code:
+       /*
+        * It is possible that we haven't received prepare because it occurred
+        * before walsender reached a consistent point in which case we need to
+        * skip rollback prepared.
+        *
+        * And we also skip the FinishPreparedTransaction if we're using the
+        * Prepare Spoolfile (using_psf) because in that case there is
no matching
+        * PrepareTransactionBlock done yet.
+        */
+       if (LookupGXact(rollback_data.gid, rollback_data.prepare_end_lsn,
+                                       rollback_data.preparetime))
+       {

5) Should this be present:
+#if 1
+       /* This is just debugging, for confirmation the update worked. */
+       {
+               Subscription *new_s;
+
+               StartTransactionCommand();
+               new_s = GetSubscription(MySubscription->oid, false);
+               CommitTransactionCommand();
+       }
+#endif

Regards,
Vignesh

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