DROP FUNCTION Statement
Removes a user-defined function (UDF), so that it is not available for execution during Impala SELECT or INSERT operations.
DROP [AGGREGATE] FUNCTION [IF EXISTS] [db_name.]function_name(type[, type...])
Statement type: DDL
Because the same function name could be overloaded with different argument signatures, you specify the argument types to identify the exact function to drop.
Currently, Impala UDFs and UDAs are not persisted in the metastore database. Information about these functions is held in the memory of the catalogd daemon. You must reload them by running the CREATE FUNCTION statements again each time you restart the catalogd daemon.
Cancellation: Cannot be cancelled.
The user ID that the impalad daemon runs under, typically the impala user, does not need any particular HDFS permissions to perform this statement. All read and write operations are on the metastore database, not HDFS files and directories.