Re: Using a User-Def function in a query

On Sep 23, 2008, at 7:50 PM, Tom Lane wrote:

> Ralph Smith <smithrn@washington.edu> writes:
>> I've written several user-defined functions (UDFs) for converting
>> dates to unix time, every which way.
>> ... but when I try to use the function in a query
>>     # select count(distinct username) from stats where eventtime >
>> dtu_dmony('22 Sep 2008') ;
>> it never comes back...
> =======================================
> Did you EXPLAIN that query?  Is it using the index I suppose you've
> got
> on eventtime?  I'll bet that it's not, and that the reason why not is
> that you didn't mark the function IMMUTABLE (or STABLE, which is the
> correct marking if it depends on the timezone setting).  The planner
> won't try to use volatile functions in index conditions.
>
>             regards, t lane
========================================

IMMUTABLE Worked!

Thank you!
Ralph