Re: proposal: set GUC variables for single query

Jan Urbański <wulczer(at)wulczer(dot)org> writes:
> this idea has cropped up last PGCon - the ability to set GUC variables
> for the duration of a single query. It would work by setting the GUCs
> for the duration of the query and setting them back to what they were
> after it has terminated. By "setting them back" I mean respecting the
> previously set values, regardless of their source (set in run-time,
> per-role settings, postgresql.conf settings).

+1 on the use case, allowing to do that in the statement itself would be
a nice convenience.

> It mostly falls into the realm of syntax sugar, but as more than one
> person felt it's a good idea, I thought I'd float it around here.
>
> I poked a little bit at the grammar to see where could it fit and didn't
> have much success of doing it without a new reserved keyword. Supposing
> the idea gets some traction, any suggestions for the syntax?

I think it would fit quite well within our extending of the WITH syntax.

WITH
work_mem = '1GB',
timezone = 'Europe/Amsterdam',
foo AS (
SELECT something
)
SELECT toplevel FROM foo;

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support