limiting resources to users

Hi:

Is there a way in Postgres to limit how much cpu, memory, other resources a certain DB gets? A MySQL DB that I'm now replacing with PG has been having problems with run-away users that pound one DB with intense processes running periodically in cron jobs. The effect is that it takes up all the resources and the users of other DBs suffer because the CPU is pegged servicing the first guy..

The PG versio will have one PG instance with many DBs. One set of these DBs are vital for operations and should have the highest priority. Another set of DBs are not vital but their users are the culprits that consume all the resources. I want to give DBs A, B, and C the highest priority, DBs D, E, F the lowest. If a DB F user is taking up all the resources, and a DB B users runs a query, I want to service the DB B guys first and backburner the DB F guy until the DB B guy is serviced first.

Thanks !