Horton

Re: make MaxBackends available in _PG_init

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, 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>
Date: 2022-04-13T13:16:10Z
Lists: pgsql-hackers 
On Tue, Apr 12, 2022 at 6:26 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
> Okay.  So maybe we only need the attached patches.  0001 is just 5ecd018
> un-reverted, and 0002 is Julien's patch from a few weeks ago with some
> minor edits.

Hmm. I suppose I was thinking that we'd go the other way around: move
the call to InitializeMaxBackends() earlier, as proposed previously,
and add a hook to allow extensions to get control before that point.
The reason that I like that approach is that I suspect that it's more
common for extensions to want to size shared memory data structures
than it is for them to want to change GUCs, and therefore I thought
that approach would fix things for the most amount of people with the
least amount of code change. But it seems like maybe Tom thinks I'm
incorrect about the relative frequency of those things, so I don't
know.

-- 
Robert Haas
EDB: http://www.enterprisedb.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