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From: Julien Rouhaud <rjuju123@gmail.com>
To: Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Amit Kapila <amit.kapila16@gmail.com>
Subject: Re: pg_upgrade and logical replication
Date: Mon, 24 Apr 2023 14:50:32 +0800
Message-ID: <20230424065032.4w7vm33qmaput3al@jrouhaud> (raw)
In-Reply-To: <TYAPR01MB5866401A4B923A07C535D59EF5999@TYAPR01MB5866.jpnprd01.prod.outlook.com>
References: <CAA4eK1+4ORS7C+j3NS9yfoKdjfpdat0XrhUy1opBvw8WN58g4Q@mail.gmail.com>
	<CAOBaU_YavOL0AhS0uU07Ea_0ZyR7youtJAvSHDnhmADGDw+VwA@mail.gmail.com>
	<CAA4eK1+pWXqDSO+QpGtLFqcCP5+qCXkvLN-YviRqdXV+d7Fdow@mail.gmail.com>
	<20230309083456.xpjcsuycyn7d2yvr@jrouhaud>
	<20230327084955.m624nwfaf7mbzo6j@jrouhaud>
	<TYAPR01MB58667340763002108CEB5EB8F5919@TYAPR01MB5866.jpnprd01.prod.outlook.com>
	<20230407022802.jqmdhgjhrnj5lpcl@jrouhaud>
	<TYAPR01MB58667233ECDB40B7FFDDB22CF59B9@TYAPR01MB5866.jpnprd01.prod.outlook.com>
	<20230413025110.gt6nahvrerngoz2m@jrouhaud>
	<TYAPR01MB5866401A4B923A07C535D59EF5999@TYAPR01MB5866.jpnprd01.prod.outlook.com>

Hi,

On Fri, Apr 14, 2023 at 04:19:35AM +0000, Hayato Kuroda (Fujitsu) wrote:
>
> I have tested, but srsublsn became NULL if copy_data was specified as off.
> This is because when copy_data is false, all tuples in pg_subscription_rels are filled
> as state = 'r' and srsublsn = NULL, and tablesync workers will never boot.
> See CreateSubscription().
> Doesn't it mean that there is a possibility that LSN option is not specified while
> ALTER SUBSCRIPTION ADD TABLE?

It shouldn't be the case for now, as pg_upgrade will check first if there's a
invalid remote_lsn and refuse to proceed if that's the case.  Also, the
remote_lsn should be set as soon as some data is replicated, so unless you add
a table that's never modified to a publication you should be able to run
pg_upgrade at some point, once there's replicated DML on such a table.

I'm personally fine with the current restrictions, but I don't really use
logical replication in any project so maybe I'm not objective enough.  For now
I'd rather keep things as-is, and later improve on it if some people want to
lift such restrictions (and such restrictions can actually be lifted).





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  Cc: rjuju123@gmail.com, kuroda.hayato@fujitsu.com, pgsql-hackers@lists.postgresql.org, amit.kapila16@gmail.com
  Subject: Re: pg_upgrade and logical replication
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