The PL/pgSQL language used for writing many types of functions is now installed in all databases by default. It can still be removed if desired. Triggers can be attached specifically to a column, eliminating unnecessary calls to trigger function that aren't needed unless specific columns are altered. It's also possible to restrict when a trigger fires using a WHEN clause, further cutting down on unnecessary calls to the trigger function.
The LISTEN/NOTIFY mechanism for passing messages between database clients is faster and allows sending a "payload" string message. This allows building some better cross-client messaging systems using the database itself than was possible before. Applications can set an application_name ...
