Re: make MaxBackends available in _PG_init

From: Nathan Bossart <nathandbossart(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(at)paquier(dot)xyz>, "Bossart, Nathan" <bossartn(at)amazon(dot)com>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, "wangsh(dot)fnst(at)fujitsu(dot)com" <wangsh(dot)fnst(at)fujitsu(dot)com>, Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, Greg Sabino Mullane <htamfids(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: make MaxBackends available in _PG_init
Date: 2022-05-06 15:27:11
Message-ID: 20220506152711.GA3404123@nathanxps13
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On Fri, May 06, 2022 at 10:43:21AM -0400, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Fri, May 6, 2022 at 9:57 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> I agree that _PG_fini functions as they stand are worthless.
>>> What I'm not getting is why we should care enough about that
>>> to break just about everybody's extension. Even if unloading
>>> extensions were feasible, who would bother?
>> Well, if we think that, then we ought to remove the NOT_USED code and
>> all the random _PG_fini() stuff that's still floating around.
> I think that's exactly what we should do, if it bugs you that stuff
> is just sitting there. I see no prospect that we'll ever make it
> work, because the question of unhooking from hooks is just the tip
> of the iceberg. As an example, what should happen with any custom
> GUCs the module has defined? Dropping their values might not be
> very nice, but if we leave them around then the next LOAD (if any)
> will see a conflict. Another fun question is whether it's ever
> safe to unload a module that was preloaded by the postmaster.
> In short, this seems like a can of very wriggly worms, with not
> a lot of benefit that would ensue from opening it.

+1, I'll put together a new patch set.

Nathan Bossart
Amazon Web Services:

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