org.apache.flink.api.common.functions

Class RichGroupReduceFunction<IN,OUT>

java.lang.Object

org.apache.flink.api.common.functions.AbstractRichFunction

org.apache.flink.api.common.functions.RichGroupReduceFunction<IN,OUT>

Type Parameters:

IN - Type of the elements that this function processes.

OUT - The type of the elements returned by the user-defined function.

All Implemented Interfaces:

Serializable, Function, GroupReduceFunction<IN,OUT>, RichFunction

Direct Known Subclasses:

GroupReduceIterator, HadoopReduceCombineFunction, HadoopReduceFunction, OperatorSubtaskStateReducer

@Public
public abstract class RichGroupReduceFunction<IN,OUT>
extends AbstractRichFunction
implements GroupReduceFunction<IN,OUT>

Rich variant of the GroupReduceFunction. As a RichFunction, it gives access to the RuntimeContext and provides setup and teardown methods: RichFunction.open(org.apache.flink.configuration.Configuration) and RichFunction.close().

Partial computation can significantly improve the performance of a RichGroupReduceFunction. This technique is also known as applying a Combiner. Implement the GroupCombineFunction interface to enable partial computation, i.e., a combiner for this RichGroupReduceFunction.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
RichGroupReduceFunction()

Method Summary

Modifier and Type	Method and Description
abstract void	reduce(Iterable<IN> values, Collector<OUT> out) The reduce method.

Methods inherited from class org.apache.flink.api.common.functions.AbstractRichFunction

close, getIterationRuntimeContext, getRuntimeContext, open, setRuntimeContext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RichGroupReduceFunction

public RichGroupReduceFunction()

Method Detail

reduce

public abstract void reduce(Iterable<IN> values,
                            Collector<OUT> out)
                     throws Exception

Description copied from interface: GroupReduceFunction

The reduce method. The function receives one call per group of elements.

Specified by:

reduce in interface GroupReduceFunction<IN,OUT>

Parameters:

values - All records that belong to the given input key.

out - The collector to hand results to.

Throws:

Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.