How to Create a New Function in ksqlDB

Custom functions are also called UDF or User Defined Function

You can create new functions by adding a jar file to the extensions directory in ksqlDB.

The extensions directory is set by the server property ksql.extension.dir.

Read how to inspect the current values for the ksqlDB properties.

Any java class within those jars annotated with @UdfDescription will be scanned for UDFs by ksqlDB at launch time.

If you implement your UDF with the name of an existing function, your new function will be used instead of the default one.

This is especially useful to overwrite or enhance default functions that come with ksqlDB.