Re: ALTER SYSTEM SET command to change postgresql.conf parameters

On 23 December 2013 19:14, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Mon, Dec 23, 2013 at 1:42 PM, Thom Brown <thom(at)linux(dot)com> wrote:
>> Discussion around this topic has reached hundreds of messages, and
>> whilst I have failed to find mention of my following question, I
>> appreciate it may have already been discussed.
>>
>> I have noticed that configuration parameters for extensions are only
>> supported if the server was started with one of the parameters already
>> being set in postgresql.conf:
>>
>> # without any mention in postgresql.conf
>> postgres=# ALTER SYSTEM SET auto_explain.log_verbose = true;
>> ERROR: unrecognized configuration parameter "auto_explain.log_verbose"
>>
>> # with auto_explain.log_verbose = false added to postgresql.conf
>> postgres=# ALTER SYSTEM SET auto_explain.log_verbose = true;
>> ALTER SYSTEM
>>
>> Removing the entry from postgresql.conf, restarting Postgres, setting
>> it to the default, then restarting again renders it unsettable again:
>>
>> # removed entry from postgresql.conf and restarted
>>
>> postgres=# ALTER SYSTEM SET auto_explain.log_verbose = default;
>> ALTER SYSTEM
>>
>> # restart postgres
>>
>> postgres=# ALTER SYSTEM SET auto_explain.log_verbose = true;
>> ERROR: unrecognized configuration parameter "auto_explain.log_verbose"
>>
>> Is this by design?
>
> I would think that you'd need to have auto_explain loaded in the
> backend where you're trying to make a change, but you shouldn't need
> the setting to be present in postgresql.conf, I would think.

This appears to be the case. I hadn't set the library to be loaded in
the config.

I guess therefore it follows that arbitrary configuration parameters
aren't supported (e.g. moo.bark = 5), only pre-defined ones.

Thanks

Thom