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

On Fri, Jun 21, 2013 at 12:56 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> On Sat, Jun 22, 2013 at 12:11 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> On Wed, Jun 19, 2013 at 1:59 PM, Peter Eisentraut <peter_e(at)gmx(dot)net> wrote:
>>> On 6/7/13 12:14 AM, Amit Kapila wrote:
>>>> I will change the patch as per below syntax if there are no objections:
>>>>
>>>> ALTER SYSTEM SET configuration_parameter {TO | =} {value, | 'value'};
>>>
>>> I do like using ALTER SYSTEM in general, but now that I think about it,
>>> the 9.3 feature to create global settings in pg_db_role_setting would
>>> also have been a candidate for exactly that same syntax if it had been
>>> available. In fact, if we do add ALTER SYSTEM, it might make sense to
>>> recast that feature into that syntax.
>>>
>>> It might be clearer to do something like ALTER SYSTEM SET EXTERNAL FILE
>>> or something like that. It's only a small syntax change, so don't worry
>>> about it too much, but let's keep thinking about it.
>>
>> I think that anything we want to add should either go before SET or
>> after the value, such as:
>>
>> ALTER SYSTEM SET configuration_parameter = 'value' IN FILE 'myconf.conf';
>> ALTER SYSTEM CONFIGURATION FILE SET configuration_parameter = 'file';
>> ALTER SYSTEM CONFIGURATION FILE 'myconf.conf' SET
>> configuration_parameter = 'file';
>>
>> I agree we shouldn't back ourselves into a syntactic corner.
>
> Maybe this idea has been already discussed, but why don't we just
> add the function like update_config_file(parameter, value)? We can
> commit the core of the patch with that function API first, and then
> we can discuss the syntax and add another API like ALTER SYSTEM
> later.
>
> We now have set_config() function to set the parameter,
> so adding the function for this feature should not be a surprise.
> If the name of the function is, for example, update_conf_file,
> most users would think that it's intuitive even if SIGHUP is not
> automatically sent immediately. We don't need to emit
> the message like 'This setting change will not be loaded until SIGHUP'.

I could certainly support that plan. I'm satisfied with the ALTER
SYSTEM syntax and feel that might find other plausible uses, but
functional notation would be OK with me, too.

--
Robert Haas
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