Horton

Re: make MaxBackends available in _PG_init

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: Nathan Bossart <nathandbossart@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, "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: 2022-04-10T23:34:09Z
Lists: pgsql-hackers 
On Sat, Apr 09, 2022 at 09:24:42PM +0800, Julien Rouhaud wrote:
> Yeah I would prefer this approach too, although it couldn't prevent extension
> from directly modifying the underlying variables so I don't know how effective
> it would be.
> 
> On the bright side, I see that citus is using SetConfigOption() to increase
> max_prepared_transactions [1].  That's the only extension mentioned in that
> thread that does modify some GUC, and this GUC was already marked as
> PGDLLIMPORT since 2017 so it probably wasn't done that way for Windows
> compatibility reason.
> 
> In the meantime, should we add an open item?

Yes, I think that we need to discuss more the matter here, so added one.
--
Michael

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