CREATE FUNCTION Statement
Confluent Cloud for Apache Flink® enables registering custom user-defined functions (UDFs) by using the CREATE FUNCTION statement. After you register your UDFs in a Flink database, you can use them in your SQL queries.
Syntax
CREATE FUNCTION <function_name>
AS <class_name>
USING JAR 'confluent-artifact://<artifact_id>'
[USING CONNECTIONS ('<connection_name>' [, ...])];
Description
Register a user-defined function (UDF) in the current database.
The optional USING CONNECTIONS clause binds one or more connection objects to the UDF, enabling external connectivity so the function can call external systems at runtime. Provide one or more connection names, separated by commas. The connection name must match the prefix that the UDF uses with FunctionContext.getJobParameter(). For example, use USING CONNECTIONS ('my_external_service') for a my_external_service.endpoint parameter.
To remove a UDF from the current database, use DROP FUNCTION.
To view the UDFs in the current database, use SHOW FUNCTIONS.
Note
UDFs are immutable. Flink has no ALTER FUNCTION or CREATE OR REPLACEFUNCTION statement, so to update a UDF, drop it and create a new function that points to the updated artifact. Dropping a function that other statements depend on can break the other statements. To ensure your statements work, see Update a UDF safely.