Jo,
> we have performance problems running several queries pon postgres 8.4 .
> Using the previous version (8.3) our queries performs well
> (The queries are quite complex, consisting of several sub-queries and
> various spatial functions).
>
> Are there some major changes from 8.3 to 8.4 that cause this bad
> performance?
Have you checked the release notes?
http://www.postgresql.org/docs/8.4/static/release-8-4.html
If you can, I'd also suggest that you show the execution plans on
8.3/8.4 on the list.
One more thing: did you also check the server configuration (work_mem, ...)?
-hannes