Date: Mon, 11 Apr 2022 13:44:42 -0700
From: Nathan Bossart <nathandbossart@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Julien Rouhaud <rjuju123@gmail.com>, Andres Freund <andres@anarazel.de>,
	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>,
	Tom Lane <tgl@sss.pgh.pa.us>,
	"pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Subject: Re: make MaxBackends available in _PG_init
Message-ID: <20220411204442.GA2004824@nathanxps13>
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On Mon, Apr 11, 2022 at 04:36:36PM -0400, Robert Haas wrote:
> On Mon, Apr 11, 2022 at 12:44 PM Nathan Bossart
> <nathandbossart@gmail.com> wrote:
>> Here are some patches.  0001 reverts all the recent commits in this area,
>> 0002 is the patch I posted in August, and 0003 is an attempt at blocking
>> GUC changes in preloaded libraries' _PG_init() functions.
> 
> If we throw an error while defining_custom_guc is true, how will it
> ever again become false?

Ah, I knew I was forgetting something this morning.

It won't, but the only place it is presently needed is when loading
shared_preload_libraries, so I believe startup will fail anyway.  However,
I can see defining_custom_guc being used elsewhere, so that is probably not
good enough.  Another approach could be to add a static
set_config_option_internal() function with a boolean argument to indicate
whether it is being used while defining a custom GUC.  I'll adjust 0003
with that approach unless a better idea prevails.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com