org.apache.flink.api.java.functions

Class SampleInCoordinator<T>

java.lang.Object

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

Type Parameters:

T - the data type wrapped in ElementWithRandom as input.

All Implemented Interfaces:

Serializable, Function, GroupReduceFunction<IntermediateSampleData<T>,T>

@Internal
public class SampleInCoordinator<T>
extends Object
implements GroupReduceFunction<IntermediateSampleData<T>,T>

SampleInCoordinator wraps the sample logic of the coordinator side (the second phase of distributed sample algorithm). It executes the coordinator side sample logic in an all reduce function. The user needs to make sure that the operator parallelism of this function is 1 to make sure this is a central coordinator. Besides, we do not need the task index information for random generator seed as the parallelism must be 1.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
SampleInCoordinator(boolean withReplacement, int numSample, long seed) Create a function instance of SampleInCoordinator.

Method Summary

Modifier and Type	Method and Description
void	reduce(Iterable<IntermediateSampleData<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

SampleInCoordinator

public SampleInCoordinator(boolean withReplacement,
                           int numSample,
                           long seed)

Create a function instance of SampleInCoordinator.

Parameters:

withReplacement - Whether element can be selected more than once.

numSample - Fixed sample size.

seed - Random generator seed.

Method Detail

reduce

public void reduce(Iterable<IntermediateSampleData<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<IntermediateSampleData<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.