Re: [RFC] Extend namespace of valid guc names

On 2013-10-04 09:57:41 -0400, Robert Haas wrote:
> On Fri, Oct 4, 2013 at 6:06 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> > It'd be pretty easy to have a function that removes everything inside a
> > certain namespace. That'd be enough to make EmitWarningsOnPlaceholders()
> > work, right?
>
> Maybe, but I don't think you're going to paper over the problem that
> easily. The GUC mechanism just isn't decided to support settings that
> pop into and out of existence like that. It's not a coincidence that
> there's no UNSET commands for GUCs. We have RESET but that means "go
> back to the default", not "go away". You're trying to bend the
> mechanism to do something that it fundamentally wasn't designed to do.
> I don't think that's the right way to go, but if we do decide to go
> in that direction it's going to take more than a trivial patch to get
> there.

But that's not a new problem? It already exists and isn't really
excerbated by this.

> > I don't really understand the resistance to the patch. It's a two line
> > change that doesn't allow anything that wasn't already allowed by other
> > means (SET, SELECT set_config(), -c). It sure isn't perfect for
> > everything but for some scenarios it improves the scenario sufficiently
> > that it'd make at least one extension author happy ;)
>
> That's true, but I think the fact that those things work is an
> oversight rather than a deliberate design decision.

Yes, but it's already being used, so, while some minor restrictions
probably aren't to problematic, forbidding multiple dots outright seems
like unnecessarily breaking user applications.

> >> Another option is to store the data in an actual table. One could
> >> have sneazle.configtable='dbname.schemaname.tablename', for example.
> >
> > Doesn't really work if your extension needs to do stuff during startup
> > tho.
>
> Granted. There's not a perfect mechanism here. But I think we should
> be devoting some thought to what a good mechanism that could be used
> by core *and* contrib would look like, rather than thinking that a
> quick hack is going to make the pain go away.

I agree that we could use some more infrastructure around configuration,
but I fail to understand why it's this patch's duty to deliver it. And I
don't see why this patch would endanger any more groundbreaking
improvements.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services