It is IMMUTABLE. I attach the output of EXPLAIN both with and without
the simple function (returning true only) in the query.
On 5/11/12 4:21 PM, Alban Hertroys wrote:
> On 11 May 2012 15:57, Inanc Seylan<inanc(dot)seylan(at)gmail(dot)com> wrote:
>> Hi all,
>>
>> I have implemented a user-defined function in C that returns a boolean value
>> after some computation. Now I have a query Q such that when I specify the
>> function in the WHERE clause of Q, Q runs in 40 secs and if I don't use the
>> function it runs in 4 secs. Then I thought that my implementation of this
>> function could be slow; so I decided to write a very simple function that
>> just returns true without any computation. To my surprise, it also takes
>> around 40 seconds to run Q with the new very simple function. Does anybody
>> have a clue about what might be going wrong?
>
> Is that a VOLATILE, STABLE or IMMUTABLE function? What's the output of
> EXPLAIN ANALYZE?