Horton

Re: make MaxBackends available in _PG_init

Michael Paquier <michael@paquier.xyz>

View thread View on postgr.es
From: Michael Paquier <michael@paquier.xyz>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: "Bossart, Nathan" <bossartn@amazon.com>, Robert Haas <robertmhaas@gmail.com>, Fujii Masao <masao.fujii@oss.nttdata.com>, "wangsh.fnst@fujitsu.com" <wangsh.fnst@fujitsu.com>, Andres Freund <andres@anarazel.de>, 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: 2022-01-29T02:19:12Z
Lists: pgsql-hackers 
On Thu, Jan 27, 2022 at 10:18:15AM -0800, Nathan Bossart wrote:
> Alright.  I think the comment adjustments still apply, so I split those out
> to a new patch.

Looks fine after a second look, so applied.

As of the issues of this thread, we really have two things to think
about:
1) How do we want to control the access of some parameters in a
context or another?  One idea would be more control through GUCs, say
with a set of context-related flags that prevent the read of some
variables until they are set.  We could encourage the use of
GetConfigOption() for that.  For MaxBackends, we could add a read-only
GUC for this purpose.  That's what Andres hinted at upthread, I
guess.
2) How do we deal with unwanted access of shared parameters?  This one
is not really controllable, is it?  And we are talking about much more
than MaxBackends.  This could perhaps be addressed with more
documentation in the headers for the concerned variables, as a first
step.
--
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