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From: Amit Kapila <amit.kapila16@gmail.com>
Date: Wed, 4 Jan 2023 18:40:41 +0530
Message-ID: <CAA4eK1LdtevYSW_Lk5MJJeCMWqQtUgKCtPkX4FNKVS-ptEBGxw@mail.gmail.com>
Subject: Re: Perform streaming logical transactions by background workers and
 parallel apply
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Masahiko Sawada <sawada.mshk@gmail.com>, 
	"wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, 
	"shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Wed, Jan 4, 2023 at 4:52 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> 2.
> + * Since the database structure (schema of subscription tables, constraints,
> + * etc.) of the publisher and subscriber could be different, applying
> + * transactions in parallel mode on the subscriber side can cause some
> + * deadlocks that do not occur on the publisher side.
>
> I think this paragraph needs to be rephrased a bit.  It is saying that
> some deadlock can occur on subscribers which did not occur on the
> publisher.  I think what it should be conveying is that the deadlock
> can occur due to concurrently applying the conflicting/dependent
> transactions which are not conflicting/dependent on the publisher due
> to <explain reason>.  Because if we create the same schema on the
> publisher it might not have ended up in a deadlock instead it would
> have been executed in sequence (due to lock waiting). So the main
> point we are conveying is that the transaction which was independent
> of each other on the publisher could be dependent on the subscriber
> and they can end up in deadlock due to parallel apply.
>

How about changing it to: "We have a risk of deadlock due to
parallelly applying the transactions that were independent on the
publisher side but became dependent on the subscriber side due to the
different database structures (like schema of subscription tables,
constraints, etc.) on each side.

-- 
With Regards,
Amit Kapila.