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 9:34 PM, Bruce Momjian <bruce@momjian.us> wrote:
> On Thu, Aug 22, 2013 at 08:36:37AM -0400, Stephen Frost wrote:
>> * Amit Kapila (amit.kapila16@gmail.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.
  Right, I also think that as file and location are fixed, so it can
be detected with name.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com