PostgreSQL users have the option of extending the set of functions and operators available. If you have a common SQL or programmatic
routine, custom functions can be an effective way to more succinctly and efficiently accomplish your tasks. Likewise, custom
operators can be created to call these functions (or existing built-in functions) in order to make more efficient and legible
Functions and operators each exist as database objects, and are thus tied to a specific database. Creating a function
while connected to the booktown database, for example, creates a function object available
only to users connected to booktown.
If you intend to re-use some general functions or operators in multiple databases, you should create them in the
template1 database. This will clone the function and operator objects from
template1 when a new database is created.
The following sections cover the creation, use, and removal of custom functions and operators.