UDF API methods

A user defined function is the most commonly used type of UDX.

A UDF is generally used in the SELECT and WHERE clauses of a SQL statement. The Appendix contains several UDF examples. In the SQL statement shown below, the UDF named "testudf" is shown in the SELECT and WHERE clauses of the statement.

select x, y, testudf(x,y)
from foo
where testudf(x,y) > 100

The methods that must be implemented to create a UDF are getName(), getType(), getArgs(), evaluate(), and getResult(). The optional methods that can be used in a UDF are calculateSize(), getOptions(), initialize(), and finalize().