Re: Re: ALTER SYSTEM SET command to change postgresql.conf parameters (RE: Proposal for Allow postgresql.conf values to be changed via SQL [review])

On 2013-08-01 20:45:38 -0400, Stephen Frost wrote:
> * Andres Freund (andres(at)2ndquadrant(dot)com) wrote:
> > I personally consider readers of this list persons... And even people
> > not interested in internals will have to look in there if they set
> > something stupid before. Like setting max_connections higher than the
> > currently configured kernel's max number of semaphores. Or a good number
> > of other settings.
>
> And that's actually one of the issues that I have with this overall
> approach.. If configurations can be set in 'data' areas which prevent
> the system from starting, that's *bad*. Very bad. It means people will
> not be able to trust PG to manage the configuration sanely and will have
> a lot of distrust and fear of the ALTER SYSTEM capability.

I agree that we need to do reasonable checks, like running GUC
validators, but we simply can't control the overall system state. And
it's not like this are errors that you couldn't get before. And we
should (that's something to improve on) report the relevant guc + file
in many cases.

> Requiring users to go monkey around inside of a system data directory to
> clean things up in order to get PG to come up is a situation we should
> do our best to prevent from ever happening.

Even trying to do this completely will guarantee that this patch will
never, ever, suceed. There simply is no way to reliably detect problems
that have complex interactions with the rest of the system.

We can improve the detection rate of problems after some real world
experience. Don't make this unneccesarily complex.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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