RE: Protect syscache from bloating with negative cache entries

From: Robert Haas [mailto:robertmhaas@gmail.com]
> On Thu, Jan 24, 2019 at 10:02 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > 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.

+1 for a separate patch for remote session configuration.  ALTER SYSTEM + SIGHUP targeted at a particular backend would
doif the DBA can log into the database server (so, it can't be used for DBaaS.)  It would be useful to have
pg_reload_conf(pid).


Regards
Takayuki Tsunakawa