org.apache.hadoop.mapreduce.lib.partition

クラス RehashPartitioner<K,V>

java.lang.Object

org.apache.hadoop.mapreduce.Partitioner<K,V>

org.apache.hadoop.mapreduce.lib.partition.RehashPartitioner<K,V>

@InterfaceAudience.Public
 @InterfaceStability.Stable
public class RehashPartitioner<K,V>
extends Partitioner<K,V>

This partitioner rehashes values returned by Object.hashCode() to get smoother distribution between partitions which may improve reduce reduce time in some cases and should harm things in no cases. This partitioner is suggested with Integer and Long keys with simple patterns in their distributions.

導入されたバージョン:

2.0.3

コンストラクタのサマリー

コンストラクタ

コンストラクタと説明
RehashPartitioner()

メソッドのサマリー

修飾子とタイプ	メソッドと説明
int	getPartition(K key, V value, int numReduceTasks) Rehash Object.hashCode() to partition.

クラスから継承されたメソッド java.lang.Object

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

コンストラクタの詳細

RehashPartitioner

public RehashPartitioner()

メソッドの詳細

getPartition

public int getPartition(K key,
                        V value,
                        int numReduceTasks)

Rehash Object.hashCode() to partition.

定義:

getPartition クラス内 Partitioner<K,V>

パラメータ:

key - the key to be partioned.

value - the entry value.

numReduceTasks - the total number of partitions.

戻り値:

the partition number for the key.