org.apache.flink.api.java.functions

Annotation Type RichGroupReduceFunction.Combinable

@Retention(value=RUNTIME)
@Target(value=TYPE)
public static @interface RichGroupReduceFunction.Combinable

This annotation can be added to classes that extend RichGroupReduceFunction, in oder to mark them as "combinable". The system may call the RichGroupReduceFunction.combine(Iterable, Collector) method on such functions, to pre-reduce the data before transferring it over the network to the actual group reduce operation.

Marking combinable functions as such is in general beneficial for performance.