Re: Index on immutable function call

On Tue, Jan 19, 2010 at 07:40:00AM +0100, Philippe Lang wrote:
> I'm trying to figure out how to use an index on an immutable function
> call in order to speed up queries.
[..]
> Unfortunately, Postgreql does not use the index at all.

Yup, an index isn't going to be very useful in what you're doing.  It's
arranged the "wrong" way around---you want something in the table itself
to compare against.  I'd just have another column in the table that
stores the result of the function call (use a trigger to keep it up to
date) and then create an index on this column if you want/need.

--
  Sam  http://samason.me.uk/