This part is about extending the server functionality with user-defined functions, data types, triggers, etc. These are advanced topics which should probably be approached only after all the other user documentation about
has been understood. Later chapters in this part describe the server-side programming languages available in the
distribution as well as general issues concerning server-side programming languages. It is essential to read at least the earlier sections of
(covering functions) before diving into the material about server-side programming languages.