Re: Protect syscache from bloating with negative cache entries

On Thu, Jan 24, 2019 at 10:02 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > On Thu, Jan 24, 2019 at 06:39:24PM +0900, Kyotaro HORIGUCHI wrote:
> >> I also thought that there's some other features that is useful if
> >> it could be turned on remotely so the remote GUC feature but it
> >> was too complex...
>
> > Well, I am thinking if we want to do something like this, we should do
> > it for all GUCs, not just for this one, so I suggest we not do this now
> > either.
>
> I will argue hard that we should not do it at all, ever.
>
> There is already a mechanism for broadcasting global GUC changes:
> apply them to postgresql.conf (or use ALTER SYSTEM) and SIGHUP.
> I do not think we need something that can remotely change a GUC's
> value in just one session. The potential for bugs, misuse, and
> just plain confusion is enormous, and the advantage seems minimal.

I think there might be some merit in being able to activate debugging
or tracing facilities for a particular session remotely, but designing
something that will do that sort of thing well seems like a very
complex problem that certainly should not be sandwiched into another
patch that is mostly about something else. And if we ever get such a
thing I suspect it should be entirely separate from the GUC system.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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