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

On Wed, Aug 28, 2013 at 02:30:41PM -0400, Stephen Frost wrote:
> * Bruce Momjian (bruce(at)momjian(dot)us) wrote:
> > On Tue, Aug 27, 2013 at 09:04:00AM +0530, Amit Kapila wrote:
> > > > I really hate the idea that someone could configure 'X' in
> > > > postgresql.conf and because the auto.conf line is later in the file,
> > > > it's able to override the original setting. Does not strike me as
> > > > intuitive at all.
> > >
> > > This is currently how include mechanism works in postgresql.conf,
> > > changing that for this special case can be costly and moreover the
> > > specs for this patch were layout from beginning that way.
> >
> > Agreed. If you are worried about ALTER SYSTEM changing postgresql.conf
> > settings, you should move the include_auto line to the top of
> > postgresql.conf, but I don't think that should be the default.
>
> While I appreciate that there are bootstrap-type issues with this, I
> really don't like this idea of "later stuff can just override earlier
> stuff".
>
> include files and conf.d-style options are for breaking the config up,
> not to allow you to override options because a file came later than an
> earlier file. Our particular implementation of config-file reading
> happens to lend itself to later-definition-wins, but that's really
> counter-intuitive for anyone unfamiliar with PG, imv.

Agreed, but I think this is a much larger issue than ALTER SYSTEM SET.

I think changing behavior to first-seen would only add to confusion.
What we really need is a WARNING when a later postgresql.conf setting
overrides an earlier one, and ALTER SYSTEM SET's config file could
behave the same, so you would know right away when you were overriding
something in postgresql.conf that appeared earlier.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +