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
Streaming Concepts # Flink’s Table API and SQL support are unified APIs for batch and stream processing. This means that Table API and SQL queries have the same semantics regardless whether their input is bounded batch input or unbounded stream input. The following pages explain concepts, practical limitations, and stream-specific configuration parameters of Flink’s relational APIs on streaming data. State Management # Table programs that run in streaming mode leverage all capabilities of...| nightlies.apache.org
Joins # Batch Streaming Flink SQL supports complex and flexible join operations over dynamic tables. There are several different types of joins to account for the wide variety of semantics queries may require. By default, the order of joins is not optimized. Tables are joined in the order in which they are specified in the FROM clause. You can tweak the performance of your join queries, by listing the tables with the lowest update frequency first and the tables with the highest update frequen...| nightlies.apache.org