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@sss.pgh.pa.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
