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From: Justin Pryzby <pryzby@telsasoft.com>
To: Nitin Jadhav <nitinjadhavpostgres@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Stephen Frost <sfrost@snowman.net>
Cc: Magnus Hagander <magnus@hagander.net>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: when the startup process doesn't
Date: Wed, 9 Jun 2021 11:19:18 -0500
Message-ID: <20210609161918.GY16435@telsasoft.com> (raw)
In-Reply-To: <CAMm1aWacYkDD5cGyhNYD_nqjD94vxSTPA_1UZdO+Em94POTgyw@mail.gmail.com>
References: <633337.1618945018@sss.pgh.pa.us>
	<20210420203642.nvxvolm37f2k6prj@alap3.anarazel.de>
	<20210421183624.GP20766@tamriel.snowman.net>
	<20210421193605.cubavrq7q5bqkf4i@alap3.anarazel.de>
	<20210422010919.4b655015@firost>
	<CAMm1aWYAjwui2OrY6TSvVF8N9YLdRdnO5BUS-t5GDR60X1FanQ@mail.gmail.com>
	<20210606222305.GZ14099@telsasoft.com>
	<CA+TgmoaG+FzfoWi3dkvZM48256vmE0CZnppgGjq6EiPw=f4OpQ@mail.gmail.com>
	<867286.1623073349@sss.pgh.pa.us>
	<CAMm1aWacYkDD5cGyhNYD_nqjD94vxSTPA_1UZdO+Em94POTgyw@mail.gmail.com>

On Wed, Jun 09, 2021 at 05:09:54PM +0530, Nitin Jadhav wrote:
> > +               {"log_min_duration_startup_process", PGC_SUSET, LOGGING_WHEN,
> >
> > I think it should be PGC_SIGHUP, to allow changing it during runtime.
> > Obviously it has no effect except during startup, but the change will be
> > effective if the current process crashes.
> > See also: https://www.postgresql.org/message-id/20210526001359.GE3676@telsasoft.com
> 
> I did not get exactly how it will change behaviour. In my
> understanding, when the server restarts after a crash, it fetches the
> value from the config file. So if there is any change that gets
> affected. Kindly correct me if I am wrong.

I don't think so.  I checked and SelectConfigFiles is called only once to read
config files and cmdline args.  And not called on restart_after_crash.

The GUC definitely isn't SUSET, since it's not useful to write in a (super)
user session SET log_min_duration_startup_process=123.

I've triple checked the behavior using a patch I submitted for Thomas' syncfs
feature.  ALTER SYSTEM recovery_init_sync_method=syncfs was not picked up when
I sent SIGABRT.  But with my patch, if I also do SELECT pg_reload_conf(), then
a future crash uses syncfs.
https://www.postgresql.org/message-id/20210526001359.GE3676@telsasoft.com

-- 
Justin





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  Cc: pryzby@telsasoft.com, nitinjadhavpostgres@gmail.com, tgl@sss.pgh.pa.us, robertmhaas@gmail.com, andres@anarazel.de, sfrost@snowman.net, magnus@hagander.net, thomas.munro@gmail.com
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