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

Le vendredi 2 août 2013 09:23:17, Amit Kapila a écrit :
> On Friday, August 02, 2013 8:57 AM Stephen Frost wrote:
> > * Andres Freund (andres(at)2ndquadrant(dot)com) wrote:
> > > FWIW, I think you've just put the final nail in the coffin of this
> > > patch by raising the barriers unreasonably high.
> >
> > For my 2c, I don't think it's an unreasonable idea to actually
> > *consider* what options are available through this mechanism rather
> > than just presuming that it's a good idea to be able to modify
> > anything, including things that you wouldn't be able to fix after a
> > restart w/o hacking around in $PGDATA.
>
> I think if user has set any value wrong such that it doesn't allow server
> to start,
> we can provide an option similar to pg_resetxlog to reset the auto file.

While guessing what changes are safe is hard, it is easy to discover the GUCs
preventing PostgreSQL from restarting correctly.
pg_ctl might be able to expose a clear message like :
MSG: Params X and Y set by ALTER SYSTEM prevent PostgreSQL from starting
HINT: Issue pg_ctl --ignore-bad-GUC start

Note that the same may also allow postgresql to start with bad GUC value in
postgresql.conf ....
So this is another topic (IMHO).

With the current idea of one-GUC-one-file in a PGDATA subdirectory it is *easy*
to fix for any DBA or admin. However, note that I do prefer a simple
'include_auto_conf=here|start|end|off' in postgresql.conf (by default at end of
file, with value 'end' set).

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