Adding audit trail fields and triggers to all tables

I need to add the following fields to all tables to existing 8.1 database:


created timestamp without time zone DEFAULT CURRENT_TIMESTAMP NOT NULL,

createdby text DEFAULT CURRENT_USER,

updated timestamp without time zone DEFAULT CURRENT_TIMESTAMP NOT NULL,

updatedby text   -- current_user who last updates this record


I need also to add triggers so that updated and updatedby fields ae
automatically set when record is changed.


Where to find script which implements this ?


Andrus.