Horton

Re: make MaxBackends available in _PG_init

Nathan Bossart <bossartn@amazon.com>

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From: "Bossart, Nathan" <bossartn@amazon.com>
To: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2021-08-03T23:13:26Z
Lists: pgsql-hackers

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On 8/2/21, 4:02 PM, "Bossart, Nathan" <bossartn@amazon.com> wrote:
> On 8/2/21, 3:42 PM, "Andres Freund" <andres@anarazel.de> wrote:
>> I've wondered, independent of this thread, about not making MaxBackends
>> externally visible, and requiring a function call to access it. It should be
>> easier to find cases of misuse if we errored out when accessed at the wrong
>> time. And we could use that opportunity to add flags that determine which
>> types of backends are included (e.g. not including autovac, or additionally
>> including aux workers or prepared xacts).
>
> I'm not opposed to this.  I can work on putting a patch together if no
> opposition materializes.

Here is a first attempt.

Nathan

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