Killing long-running queries

[Dan Harris <fbsd@xxxxxxxxxxxxxxx>]

My database is used primarily in an OLAP-type environment.  Sometimes my 
users get a little carried away and find some way to slip past the 
sanity filters in the applications and end up bogging down the server 
with queries that run for hours and hours.  And, of course, what users 
tend to do is to keep queuing up more queries when they don't see the 
first one return instantly :)

So, I have been searching for a way to kill an individual query.  I read 
in the mailing list archives that you could 'kill' the pid.  I've tried 
this a few times and more than once, it has caused the postmaster to 
die(!), terminating every query that was in process, even unrelated to 
that query. 

Is there some way I can just kill a query and not risk breaking 
everything else when I do it?

Thanks