Impala User-Defined Functions

A user-defined function (UDF) is a SQL function that you create to encapsulate code that processes column values during an Impala query. UDFs are called from within a SQL statement, like a regular function, and return a single value. Starting in Impala 1.2.3 for MapR, you can create UDFs to perform custom calculations and transformations that built-in SQL operators and functions do not provide.

After you download and install the UDF development package, you can write your own UDFs and invoke them in the queries that you run on Impala. Impala can run scalar UDFs and UDAFs (user-defined aggregate functions).
Note: User-defined functions written in C++ persist when the catalog service is restarted. You no longer have to run the CREATE FUNCTION statements again after a restart. You must still reissue the CREATE FUNCTION statement for any Java-based user-defined functions.