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

On Thu, Aug 22, 2013 at 08:36:37AM -0400, Stephen Frost wrote:
> * Amit Kapila (amit(dot)kapila16(at)gmail(dot)com) wrote:
> > This can resolve the problem of whether to read auto file rather
> > cleanly, so the idea is:
> >
> > Enable/Disable reading of auto file
> > -----------------------------------------------------
> > a. Have a new include in postresql.conf
> > #include_auto_conf_file postgresql.auto.conf
> > as it is a special include, we can read this file relative to data
> > directory.

The big advantage of using 'include_auto_conf_file' and not simply
'include' is that we can issue an error from ALTER SYSTEM SET if that is
not set.

> > Enable/Disable Alter System command
> > -----------------------------------------------------------
> > This can be achieved in 3 ways:
> > a. Check before executing Alter System if include directive is
> > disabled, then just issue a warning to user and proceed with command.
> > b. Check before executing Alter System if include directive is
> > disabled, then just issue an error and stop.
>
> It doesn't make sense for it to be a 'warning' with this- the
> parameter specifies the file to use. If you don't know what file to
> use, how you can possibly do anything but return an error?

Agreed. No sense in allowing users to add things to the 'auto' file
when the auto file is inactive.

> Note that I *like* that about this approach.
>
> There are a few other considerations with this-
>
> - What should the default be? (Still thinking 'off' myself)

Probably, but we might need to wait until we have a final API for a
decision on that.

> - What happens if the user specifies 'postgresql.conf'? I'm thinking we
> would disallow such insanity (as that's what it is, imv..) by having
> an identifier in the file that this is the PG "auto conf" file.

I am thinking they can't include a value equal to 'config_file', which
is normally postgresql.conf. I am not a big fan of looking for special
text in files. This might be complex to check, though, because of path
changes --- we might just disallow the basement from matching the
basename of config_file.

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

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