From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Davis <pgsql@j-davis.com>
cc: pgsql-bugs@postgresql.org
Subject: Re: [15] Custom WAL resource managers, single user mode, and recovery
In-reply-to: <9decc18a42634f8a2f15c97a385a0f51a752f396.camel@j-davis.com>
References: <9decc18a42634f8a2f15c97a385a0f51a752f396.camel@j-davis.com>
Comments: In-reply-to Jeff Davis <pgsql@j-davis.com>
	message dated "Thu, 14 Jul 2022 17:22:54 -0700"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <3192873.1657846137.1@sss.pgh.pa.us>
Date: Thu, 14 Jul 2022 20:48:57 -0400
Message-ID: <3192874.1657846137@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/3192874.1657846137%40sss.pgh.pa.us>
Precedence: bulk

Jeff Davis <pgsql@j-davis.com> writes:
> If a user has custom table access methods, those are likely to be
> required during single user mode anyway (to VACUUM, for instance), so
> we need to be able to load modules during single user mode. I can't
> think of a reason specifically why we can't process
> shared_preload_libraries. Thoughts?

Hmm.  There may have been some idea that a library might fail in
single-user mode, and/or have been the cause of you needing to
use single-user in the first place.  But if so, you can always
edit it out of shared_preload_libraries.  I agree that not
having the option to load it isn't great.

I think that the patch might be missing some stuff.  In postmaster.c,
there are several steps after process_shared_preload_libraries()
that look to be there to support loadable libraries, such as
process_shmem_requests().  Wouldn't it be reasonable to expect
that a loadable library would malfunction without those?

(I wonder if we shouldn't refactor this so that the postmaster
and standalone mode share more of the initialization logic.
Keeping these bits in sync seems unlikely to happen otherwise.)

			regards, tom lane