From: Tom Lane <tgl@sss.pgh.pa.us>
To: Nathan Bossart <nathandbossart@gmail.com>
cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>,
        Julien Rouhaud <rjuju123@gmail.com>,
        Michael Paquier <michael@paquier.xyz>,
        "Bossart,
    Nathan" <bossartn@amazon.com>,
        Fujii Masao <masao.fujii@oss.nttdata.com>,
        "wangsh.fnst@fujitsu.com" <wangsh.fnst@fujitsu.com>,
        Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>,
        Greg Sabino Mullane <htamfids@gmail.com>,
        "pgsql-hackers@lists.postgresql.org"
 <pgsql-hackers@lists.postgresql.org>
Subject: Re: make MaxBackends available in _PG_init
In-reply-to: <20220412194938.GA2064338@nathanxps13>
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Comments: In-reply-to Nathan Bossart <nathandbossart@gmail.com>
	message dated "Tue, 12 Apr 2022 12:49:38 -0700"
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Date: Tue, 12 Apr 2022 16:33:39 -0400
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Nathan Bossart <nathandbossart@gmail.com> writes:
> On Tue, Apr 12, 2022 at 03:12:42PM -0400, Robert Haas wrote:
>> But if there's even one use case where adjusting GUCs at this phase is
>> reasonable, then 0003 isn't really good enough. We need an 0004 that
>> provides a new hook in a place where such changes can safely be made.

> I think that is doable.  IMO it should be ѕomething like _PG_change_GUCs()
> that is called before _PG_init().  The other option is to add a hook called
> after _PG_init() where MaxBackends is available (in which case we likely
> want GetMaxBackends() again).  Thoughts?

I like the second option.  Calling into a module before we've called its
_PG_init function is just weird, and will cause no end of confusion.

			regards, tom lane