Resource management in 7.4

Hi all,

I've been thinking about resource management and postgres. I want to
develop a user profile system (a-la oracle) which allows a DBA to
restrict/configure access to system resources. This would allow a DBA to
configure how much CPU time can be used per query/session for any user,
the number blocks that can be read/written by a user per query, and
perhaps some other things (see below).

Current, Postgres allows us to trivial calculate the following: CPU time
for a given query (and as such, CPU time for a session), file system
blocks read in/out for a given query (and therefore, for a given session),
and some other stuff. The question is, given access to this information,
how regularly should we check to see if the user has passed the set
limits? My concern is that if we check too regularly, we impact upon
performance. Also, should we be intelligent about it (would hate to error
out of a select when we believe that there is only a small number of
tuples left)?

There are some other resource management features which would be
useful: number of sessions per user, maximum memory usage per user,
maximum disk space for temp files, etc. Oracle supports things like
maximum time in parser, planner and executor, maximum memory blocks
accessed. I think that maximum sessions per user would be useful but the
other ones seem like more trouble than they're worth. Have I missed
any resources here?

Gavin