Do you mean in a select statement? Such as:
SELECT func(date) as month, count(*) FROM foo GROUP BY month;
Or even:
SELECT count(*) FROM foo GROUP BY func(date);
The first is supported. The second would require some changes to the parser.
De Clarke wrote:
> I didn't realize PG could not do
>
> group by [function on column]
>
> Ouch!
>