Postgresql – How to monitor PostgreSQL queries

I try to stay away from having multiple databases in one instance. Instead I have multiple instances set up on a server where each one is dedicated to a database.

MySQL Cacti templates are a good monitoring solution. If you are enterprise customer then MySQL Enterprise Monitor works. Also check out mycheckpoint from openark.

EDIT
Here are some tutorials for setting up multiple instances on one server:

• Running multiple instances of MySQL on the same machine
• How-to: Setup Multiple MySQL Instances

You could also use MySQL Sandbox as it automates a lot of different set ups for you.

You might want to look into AUDIT ALL STATEMENTS BY user. As per Oracle's documentation, audit all statements by ... audits all top-level SQL statements executed. Top-level SQL statements are issued directly by a user. SQL statements run from within a PL/SQL procedure or function are not considered top-level statements. Therefore, this clause does not audit the statements executed within PL/SQL procedures or functions. However, the execution of the PL/SQL procedure or function itself is audited. This clause is useful if you want to audit all the statements in a specific environment, regardless of other auditing configurations that are system wide or user specific.