REFRESH FUNCTIONS Statement
In CDH 5.12 / Impala 2.9 and higher, you can run the REFRESH FUNCTIONS statement to refresh the user-defined functions (UDFs) created outside of Impala. For example, you can add Java-based UDFs to the metastore database through the Hive CREATE FUNCTION statements and make those UDFs visible to Impala at the database level by subsequently running REFRESH FUNCTIONS.
The REFRESH FUNCTIONS statement is only required if you create or modify UDFs from outside of Impala. Updated metadata, as a result of running REFRESH FUNCTIONS, is broadcast to all Impala coordinators.
Once issued, the REFRESH FUNCTIONS statement cannot be cancelled.
REFRESH FUNCTIONS db_name