User-defined Functions # User-defined functions (UDFs) are extension points to call frequently used logic or custom logic that cannot be expressed otherwise in queries. User-defined functions can be implemented in a JVM language (such as Java or Scala) or Python. An implementer can use arbitrary third party libraries within a UDF. This page will focus on JVM-based languages, please refer to the PyFlink documentation for details on writing general and vectorized UDFs in Python.
