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.| nightlies.apache.org
Time Attributes # Flink can process data based on different notions of time. Processing time refers to the machine’s system time (also known as epoch time, e.g. Java’s System.currentTimeMillis()) that is executing the respective operation. Event time refers to the processing of streaming data based on timestamps that are attached to each row. The timestamps can encode when an event happened. For more information about time handling in Flink, see the introduction about event time and water...| nightlies.apache.org