Re: index usage

["Daniel Caune" <daniel(dot)caune(at)ubisoft(dot)com>]

> De : pgsql-performance-owner(at)postgresql(dot)org [mailto:pgsql-performance-
> owner(at)postgresql(dot)org] De la part de Ben
> Envoyé : vendredi, juillet 28, 2006 15:21
> À : pgsql-performance(at)postgresql(dot)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