Re: Proposal for Allow postgresql.conf values to be changed via SQL

On Wed, Nov 7, 2012 at 12:29 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Magnus Hagander <magnus@hagander.net> writes:
>> On Wed, Nov 7, 2012 at 6:19 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> You could dig it out of the stack if it's there, but that doesn't fix
>>> the race-condition aspect.  Now a race is inevitable if two sessions try
>>> to set the *same* variable, but I think people will be unhappy if a SET
>>> on one variable makes a recent SET on some other variable disappear.
>
>> I think if we require an exclusive lock on a single global lock for
>> "set permanent", people are quite ok with that, really.
>
> That doesn't fix it either, at least not without a whole lot of other
> changes --- we don't normally read the config file within-commands,
> and there are both semantic and implementation problems to overcome
> if you want to do so.

Why would you need to?  It seems to me that we ought to be able to
rewrite a machine-generated configuration file without loading those
values into the current session.  If we can't, that seems like prima
facie evidence that the format is not sufficiently easy to
machine-parse.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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