I want to profile (keep an Eye on) all the activities that goes on in a Database which is in PostgreSQL.
Is there any such utility which will help me do this?
"Keep an eye on" and "profile" are two quite different tasks in my view.
For profiling (not a live view on what's going on right now, but to see which queries take most time etc), check out pgFouine:
http://pgfouine.projects.postgresql.org/
This will let you see which queries are resource intensive, and take appropriate action: Add missing indexes, rewrite queries using other techiques etc.
Since rebra answer another profiling tool pgbadger went out.
You can find it here:
http://dalibo.github.io/pgbadger/
you can get a very detailed report and graphs.
pgfouine is not maintained anymore, last update was in 2010.
Well, if you're looking at what's going on, regarding selects, updates, deletes, and so on, there are a few views in the pg_catalog schema, I mainly use pg_stat_user_tables and pg_stat_user_indexes but there are many more, all within pg_stat*.
There also is the pg_stat_activity view which tells you what's running on your server right now.
I've hacked together four munin plugins that uses the user_tables and user_indexes, they're available there