Removes a user-defined function (UDF), so that it is not available for execution during Impala
SELECT or INSERT operations.
Syntax:
To drop C++ UDFs and UDAs:
DROP [AGGREGATE] FUNCTION [IF EXISTS] [db_name.]function_name(type[, type...])
The preceding syntax, which includes the function signature, also applies to Java UDFs that were created
using the corresponding CREATE FUNCTION syntax that includes the argument and return types.
After upgrading to Impala 2.5 or higher, consider re-creating all Java UDFs with the
CREATE FUNCTION syntax that does not include the function signature. Java UDFs created this
way are now persisted in the metastore database and do not need to be re-created after an Impala restart.
To drop Java UDFs (created using the CREATE FUNCTION syntax with no function signature):
DROP FUNCTION [IF EXISTS] [db_name.]function_nameStatement type: DDL
Usage notes:
Because the same function name could be overloaded with different argument signatures, you specify the argument types to identify the exact function to drop.
Restrictions:
In Impala 2.5 and higher, Impala UDFs and UDAs written in C++ are
persisted in the metastore database. Java UDFs are also persisted, if they were created
with the new CREATE FUNCTION syntax for Java UDFs, where the Java
function argument and return types are omitted. Java-based UDFs created with the old
CREATE FUNCTION syntax do not persist across restarts because they are
held in the memory of the catalogd daemon. Until you re-create such
Java UDFs using the new CREATE FUNCTION syntax, you must reload those
Java-based UDFs by running the original CREATE FUNCTION statements
again each time you restart the catalogd daemon. Prior to
Impala 2.5 the requirement to reload functions after a restart
applied to both C++ and Java functions.
Cancellation: Cannot be cancelled.
HDFS permissions:
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.
Examples:
The following example shows how to drop Java functions created with the signatureless
CREATE FUNCTION syntax in Impala 2.5 and higher.
Issuing DROP FUNCTION function_name removes all the
overloaded functions under that name.
(See CREATE FUNCTION Statement for a longer example
showing how to set up such functions in the first place.)
create function my_func location '/user/impala/udfs/udf-examples.jar'
symbol='org.apache.impala.TestUdf';
show functions;
+-------------+---------------------------------------+-------------+---------------+
| return type | signature | binary type | is persistent |
+-------------+---------------------------------------+-------------+---------------+
| BIGINT | my_func(BIGINT) | JAVA | true |
| BOOLEAN | my_func(BOOLEAN) | JAVA | true |
| BOOLEAN | my_func(BOOLEAN, BOOLEAN) | JAVA | true |
...
| BIGINT | testudf(BIGINT) | JAVA | true |
| BOOLEAN | testudf(BOOLEAN) | JAVA | true |
| BOOLEAN | testudf(BOOLEAN, BOOLEAN) | JAVA | true |
...
drop function my_func;
show functions;
+-------------+---------------------------------------+-------------+---------------+
| return type | signature | binary type | is persistent |
+-------------+---------------------------------------+-------------+---------------+
| BIGINT | testudf(BIGINT) | JAVA | true |
| BOOLEAN | testudf(BOOLEAN) | JAVA | true |
| BOOLEAN | testudf(BOOLEAN, BOOLEAN) | JAVA | true |
...
Related information: