It's volatile, but it will always return an integer.
On Fri, 28 Jul 2006, Daniel Caune wrote:
>> De : pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-
>> owner@postgresql.org] De la part de Ben
>> Envoyé : vendredi, juillet 28, 2006 15:21
>> À : pgsql-performance@postgresql.org
>> Objet : [PERFORM] index usage
>>
>> I have a table with 37000 rows, an integer column, and an index on that
>> column. I've got a function that returns an integer. When I do a select
>> where I restrict that column to being equal to a static number, explain
>> tells me the index will be used. When I do the same thing but use the
>> function instead of a static number, explain shows me a full scan on the
>> table.
>>
>> I must be missing something, because my understanding is that the function
>> will be evaluated once for the statement and then collapsed into a static
>> number for the filtering. But the results of the explain seem to imply
>> that's not the case....?
>>
>
> Is your function IMMUTABLE, STABLE or VOLATILE?
>
> --
> Daniel
>
