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From: [email protected] <[email protected]>
To: Hayato Kuroda (Fujitsu) <[email protected]>
Cc: Masahiko Sawada <[email protected]>
Cc: [email protected] <[email protected]>
Cc: Peter Smith <[email protected]>
Cc: Dilip Kumar <[email protected]>
Cc: [email protected] <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: RE: Perform streaming logical transactions by background workers and parallel apply
Date: Sun, 27 Nov 2022 04:16:15 +0000
Message-ID: <OS0PR01MB571623B343E30E0219F4B86194109@OS0PR01MB5716.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <TYAPR01MB5866051F824309A2B50737ECF50D9@TYAPR01MB5866.jpnprd01.prod.outlook.com>
References: <CAA4eK1JQTDXTfvJ5d+L0ggG4+doyd0Xji=e0OJsb=qcn_jWALA@mail.gmail.com>
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On Tuesday, November 22, 2022 9:53 PM Kuroda, Hayato <[email protected]> wroteL
> 
> Thanks for updating the patch!
> I tested the case whether the deadlock caused by foreign key constraint could
> be detected, and it worked well.
> 
> Followings are my review comments. They are basically related with 0001, but
> some contents may be not. It takes time to understand 0002 correctly...

Thanks for the comments!

> 01. typedefs.list
> 
> LeaderFileSetState should be added to typedefs.list.
> 
> 
> 02. 032_streaming_parallel_apply.pl
> 
> As I said in [1]: the test name may be not matched. Do you have reasons to
> revert the change?

The original parallel safety check has been removed, so I changed the name.
After rethinking about this, I named it to stream_parallel_conflict.

> 
> 03. 032_streaming_parallel_apply.pl
> 
> The test does not cover the case that the backend process relates with the
> deadlock. IIUC this is another motivation to use a stream/transaction lock.
> I think it should be added.

The main deadlock cases that stream/transaction lock can detect is 1) LA->PA 2)
LA->PA->PA as explained atop applyparallelworker.c. So I think backend process
related one is a variant which I think have been covered by the existing
tests in the patch.

> 04. log output
> 
> While being applied spooled changes by PA, there are so many messages like
> "replayed %d changes from file..." and "applied %u changes...". They comes
> from
> apply_handle_stream_stop() and apply_spooled_messages(). They have same
> meaning, so I think one of them can be removed.

Changed.

> 05. system_views.sql
> 
> In the previous version you modified pg_stat_subscription system view. Why
> do you revert that?

I was not sure should we include that in the main patch set.
I added a top-up patch that change the view.

> 06. interrupt.c - SignalHandlerForShutdownRequest()
> 
> In the comment atop SignalHandlerForShutdownRequest(), some processes
> that assign the function except SIGTERM are clarified. We may be able to add
> the parallel apply worker.

Changed


> 08. guc_tables.c - ConfigureNamesInt
> 
> ```
>                 &max_sync_workers_per_subscription,
> +               2, 0, MAX_PARALLEL_WORKER_LIMIT,
> +               NULL, NULL, NULL
> +       },
> ```
> 
> The upper limit for max_sync_workers_per_subscription seems to be wrong, it
> should be used for max_parallel_apply_workers_per_subscription.

That's my miss, sorry for that.

> 10. worker.c - maybe_reread_subscription()
> 
> 
> ```
> +               if (am_parallel_apply_worker())
> +                       ereport(LOG,
> +                       /* translator: first %s is the name of logical replication
> worker */
> +                                       (errmsg("%s for subscription \"%s\"
> will stop because of a parameter change",
> +
> + get_worker_name(), MySubscription->name)));
> ```
> 
> I was not sure get_worker_name() is needed. I think "logical replication apply
> worker"
> should be embedded.

Changed.

> 
> 11. worker.c - ApplyWorkerMain()
> 
> ```
> +                               (errmsg_internal("%s for subscription \"%s\"
> two_phase is %s",
> +
> + get_worker_name(),
> ```

Changed


Best regards,
Hou zj


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