THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
Hive User-defined functions (UDFs) are custom functions that are developed in Java and integrated with Apache Hive. UDFs are routines that accept parameters, perform an action, and return the result of the action as a value. The return value can be a single scalar row or a result set, it depends on the UDF's code and implemented interface.
UDFs are powerful capability that extends the classical SQL functionality with custom code, that the Hive user can utilize. Hive has a bunch of built-in UDFs that you can utilize. Like other SQL-based solutions, Apache Hive also provides functionality to extend the current - rich- UDF set with custom if needed.
Important
Important to mention. Every UDF's evaluate method one row at a time! Which means if your UDF's has complex code, it could introduce performance issue in execution time.