Horton

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

Ajin Cherian <itsajin@gmail.com>

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From: Ajin Cherian <itsajin@gmail.com>
To: Greg Nancarrow <gregn4422@gmail.com>
Cc: Peter Smith <smithpb2250@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, vignesh C <vignesh21@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-06-23T03:39:58Z
Lists: pgsql-hackers

Attachments

On Tue, Jun 22, 2021 at 3:36 PM Greg Nancarrow <gregn4422@gmail.com> wrote:

> Some minor comments:
>
> (1)
> v88-0002
>
> doc/src/sgml/logicaldecoding.sgml
>
> "examples shows" is not correct.
> I think there is only ONE example being referred to.
>
> BEFORE:
> +    The following examples shows how logical decoding is controlled over the
> AFTER:
> +    The following example shows how logical decoding is controlled over the
>
>
fixed.

> (2)
> v88 - 0003
>
> doc/src/sgml/ref/create_subscription.sgml
>
> (i)
>
> BEFORE:
> +          to the subscriber on the PREPARE TRANSACTION. By default,
> the transaction
> +          prepared on publisher is decoded as a normal transaction at commit.
> AFTER:
> +          to the subscriber on the PREPARE TRANSACTION. By default,
> the transaction
> +          prepared on the publisher is decoded as a normal
> transaction at commit time.
>

fixed.

> (ii)
>
> src/backend/access/transam/twophase.c
>
> The double-bracketing is unnecessary:
>
> BEFORE:
> + if ((gxact->valid && strcmp(gxact->gid, gid) == 0))
> AFTER:
> + if (gxact->valid && strcmp(gxact->gid, gid) == 0)
>

fixed.

> (iii)
>
> src/backend/replication/logical/snapbuild.c
>
> Need to add some commas to make the following easier to read, and
> change "needs" to "need":
>
> BEFORE:
> + * The prepared transactions that were skipped because previously
> + * two-phase was not enabled or are not covered by initial snapshot needs
> + * to be sent later along with commit prepared and they must be before
> + * this point.
> AFTER:
> + * The prepared transactions, that were skipped because previously
> + * two-phase was not enabled or are not covered by initial snapshot, need
> + * to be sent later along with commit prepared and they must be before
> + * this point.
>

fixed.

> (iv)
>
> src/backend/replication/logical/tablesync.c
>
> I think the convention used in Postgres code is to check for empty
> Lists using "== NIL" and non-empty Lists using "!= NIL".
>
> BEFORE:
> + if (table_states_not_ready && !last_start_times)
> AFTER:
> + if (table_states_not_ready != NIL && !last_start_times)
>
>
> BEFORE:
> + else if (!table_states_not_ready && last_start_times)
> AFTER:
> + else if (table_states_not_ready == NIL && last_start_times)
>

fixed.

Also fixed comments from Vignesh:

1) This content is present in
v87-0001-Add-option-to-set-two-phase-in-CREATE_REPLICATIO.patch and
v87-0003-Add-support-for-prepared-transactions-to-built-i.patch, it
can be removed from one of them
       <varlistentry>
+       <term><literal>TWO_PHASE</literal></term>
+       <listitem>
+        <para>
+         Specify that this logical replication slot supports decoding
of two-phase
+         transactions. With this option, two-phase commands like
+         <literal>PREPARE TRANSACTION</literal>, <literal>COMMIT
PREPARED</literal>
+         and <literal>ROLLBACK PREPARED</literal> are decoded and transmitted.
+         The transaction will be decoded and transmitted at
+         <literal>PREPARE TRANSACTION</literal> time.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>

I don't see this duplicate content.

2) This change is not required, it can be removed:
   <sect1 id="logicaldecoding-example">
    <title>Logical Decoding Examples</title>
-
    <para>
     The following example demonstrates controlling logical decoding using the
     SQL interface.

fixed this.

3) We could add comment mentioning example 1 at the beginning of
example 1 and example 2 for the newly added example with description,
that will clearly mark the examples.

added this.

5) This should be before verbose, the options are documented alphabetically

fixed.this.

regards,
Ajin Cherian
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