org.apache.flink.api.java.functions

Class FirstReducer<T>

java.lang.Object

org.apache.flink.api.java.functions.FirstReducer<T>

Type Parameters:

T -

All Implemented Interfaces:

Serializable, Function, GroupCombineFunction<T,T>, GroupReduceFunction<T,T>

@Internal
public class FirstReducer<T>
extends Object
implements GroupReduceFunction<T,T>, GroupCombineFunction<T,T>

Reducer that only emits the first N elements in a group.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
FirstReducer(int n)

Method Summary

Modifier and Type	Method and Description
void	combine(Iterable<T> values, Collector<T> out) The combine method, called (potentially multiple timed) with subgroups of elements.
void	reduce(Iterable<T> values, Collector<T> out) The reduce method.

Methods inherited from class java.lang.Object

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

Constructor Detail

FirstReducer

public FirstReducer(int n)

Method Detail

reduce

public void reduce(Iterable<T> values,
                   Collector<T> 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<T,T>

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.

combine

public void combine(Iterable<T> values,
                    Collector<T> out)
             throws Exception

Description copied from interface: GroupCombineFunction

The combine method, called (potentially multiple timed) with subgroups of elements.

Specified by:

combine in interface GroupCombineFunction<T,T>

Parameters:

values - The elements to be combined.

out - The collector to use to return values from the function.

Throws:

Exception - The function may throw Exceptions, which will cause the program to cancel, and may trigger the recovery logic.