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In-Reply-To: <ea766b46-c46c-494d-adc7-b6666e9424e9@app.fastmail.com>
From: Amit Kapila <amit.kapila16@gmail.com>
Date: Tue, 24 Jan 2023 10:48:42 +0530
Message-ID: <CAA4eK1Jp-u3inupFbT+iETcRH5VwpFh__dKB5opc-O1ce+sxkw@mail.gmail.com>
Subject: Re: Time delayed LR (WAS Re: logical replication restrictions)
To: Euler Taveira <euler@eulerto.com>
Cc: "osumi.takamichi@fujitsu.com" <osumi.takamichi@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, 
	vignesh C <vignesh21@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, 
	"kuroda.hayato@fujitsu.com" <kuroda.hayato@fujitsu.com>, 
	"shveta.malik@gmail.com" <shveta.malik@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, 
	Melih Mutlu <m.melihmutlu@gmail.com>, Andres Freund <andres@anarazel.de>, 
	Marcos Pegoraro <marcos@f10.com.br>, pgsql-hackers <pgsql-hackers@postgresql.org>
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On Tue, Jan 24, 2023 at 5:02 AM Euler Taveira <euler@eulerto.com> wrote:
>
> On Sun, Jan 22, 2023, at 9:42 AM, Takamichi Osumi (Fujitsu) wrote:
>
>
> Attached the updated patch v19.
>
> [I haven't been following this thread for a long time...]
>
> Good to know that you keep improving this patch. I have a few suggestions that
> were easier to provide a patch on top of your latest patch than to provide an
> inline suggestions.
>

Euler, thanks for your comments. We have an existing problem related
to shutdown which impacts this patch. The problem is that during
shutdown on the publisher, we wait for all the WAL to be sent and
flushed on the subscriber. Now, if we user has configured a long value
for min_apply_delay on the subscriber then the shutdown won't be
successful. This can happen even today if the subscriber waits for
some lock during the apply. This is not so much a problem with
physical replication because there we have a separate process to first
flush the WAL. This problem has been discussed in a separate thread as
well. See [1]. It is important to reach conclusion even if we just
want to document it. So, your thoughts on that other thread can help
us to make it move forward.

[1] - https://www.postgresql.org/message-id/TYAPR01MB586668E50FC2447AD7F92491F5E89%40TYAPR01MB5866.jpnprd01.prod.outlook.com

-- 
With Regards,
Amit Kapila.