Horton

Re: make MaxBackends available in _PG_init

Nathan Bossart <nathandbossart@gmail.com>

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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>
Date: 2022-04-11T20:44:42Z
Lists: pgsql-hackers 
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

Commits

  1. Add a new shmem_request_hook hook.

  2. Remove non-functional code for unloading loadable modules.

  3. Fix misleading comments about background worker registration.

  4. Revert the addition of GetMaxBackends() and related stuff.

  5. Fix typo in multixact.c

  6. Reduce more the number of calls to GetMaxBackends()

  7. Remove MaxBackends variable in favor of GetMaxBackends() function.

  8. Fix comments about bgworker registration before MaxBackends initialization

  9. Fix bogus assertion in BootstrapModeMain().

  10. Make sure MaxBackends is always set