| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, "Bossart, Nathan" <bossartn(at)amazon(dot)com>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, "wangsh(dot)fnst(at)fujitsu(dot)com" <wangsh(dot)fnst(at)fujitsu(dot)com>, Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, Greg Sabino Mullane <htamfids(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: make MaxBackends available in _PG_init |
| Date: | 2022-04-12 19:59:08 |
| Message-ID: | 20220412195908.GA2064996@nathanxps13 |
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| Lists: | pgsql-hackers |
On Tue, Apr 12, 2022 at 03:30:23PM -0400, Robert Haas wrote:
> On Tue, Apr 12, 2022 at 3:22 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Yeah. It's a very long way from "changing shared memory sizes here
>> doesn't work" to "no extension is allowed to change any GUC at load
>> time". A counterexample is that it's not clear why an extension
>> shouldn't be allowed to define a GUC using DefineCustomXXXVariable
>> and then immediately set it to some other value. I think trying to
>> forbid that across-the-board is going to mostly result in breaking
>> a lot of cases that are perfectly safe.
>
> Hmm, that's an interesting case which I hadn't considered. It seems
> like sort of a lame thing to do, because why wouldn't you just create
> the GUC with the right initial value instead of modifying it after the
> fact? But maybe there's some use case in which it makes sense to do it
> that way. A read-only GUC that advertises some calculated value,
> perhaps?
I think it'd be reasonable to allow changing custom GUCs in _PG_init().
Those aren't going to impact things like MaxBackends.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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