PostgreSQL provides a large number of functions and operators
for the built-in data types. Users can also define their own
functions and operators, as described in Part V. The psql
commands \df and \do can be used to list all available functions
and operators, respectively. If you are concerned about
portability then note that most of the functions and operators
described in this chapter, with the exception of the most
trivial arithmetic and comparison operators and some explicitly
marked functions, are not specified by the SQL standard. Some of
this extended functionality is present in other SQL database
management systems, and in many cases this functionality is
compatible and consistent between the various implementations.
This chapter is also not exhaustive; additional functions appear
in relevant sections of the manual.