Re: problem with custom_variable_classes

On Wed, Sep 24, 2008 at 12:15:41PM -0400, Malcolm Studd wrote:
> I have a pl/pgSQL function[1] to calculate row numbers (based on [2]).
> It uses a custom variable. This was working earlier, but is breaking now
> saying it can't recognise the variable. The custom_variable_classes is
> set in the postgresql.conf.
> pgdb001=> select rownum('') from generate_series(1,10);
> ERROR: unrecognized configuration parameter "olap.rownum_name"
> pgdb001=> show custom_variable_classes;
> custom_variable_classes
> -------------------------
> olap
> (1 row)
> settings_id := current_setting('olap.rownum_name');

it looks like a bug to me.
it did work in 8.2, and it doesn't in 8.3, or in 8.4.

while manual in 8.4 still states:
"When custom_variable_classes is set, the server will accept definitions of arbitrary variables within each specified class.".

so it should work, but it doesn't:
# show custom_variable_classes ;
custom_variable_classes
-------------------------
depesz
(1 row)
# select current_setting('depesz.xxx');
ERROR: unrecognized configuration parameter "depesz.xxx"

of course i still can set a value, and then get it:
# select set_config('depesz.xxx', 'xx', false);
set_config
------------
xx
(1 row)
# select current_setting('depesz.xxx');
current_setting
-----------------
xx
(1 row)

but it means that there is currently no way to check if there is value in this
- i.e. if it has been initialized.

i would suggest to return "NULL" when calling current_setting on unknown variable.

this is not how it worked in 8.2 (it returned empty string), but NULL is (in my opinion) better choice.

strangely - name of "current_setting" function nor "custom_variable_classes"
doesn't show in any release docs, which makes the change somewhat mysterious.

Best regards,

depesz

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