org.apache.hadoop.mapred.lib
Class HashPartitioner<K2,V2>

java.lang.Object
  org.apache.hadoop.mapred.lib.HashPartitioner<K2,V2>

All Implemented Interfaces:

JobConfigurable, Partitioner<K2,V2>

public class HashPartitioner<K2,V2>
extends Object
implements Partitioner<K2,V2>

Partition keys by their Object.hashCode().

Constructor Summary

HashPartitioner()

Method Summary

void	configure(JobConf job) Initializes a new instance from a JobConf.
int	getPartition(K2 key, V2 value, int numReduceTasks) Use Object.hashCode() to partition.

Methods inherited from class java.lang.Object

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

Constructor Detail

HashPartitioner

public HashPartitioner()

Method Detail

configure

public void configure(JobConf job)

Description copied from interface: JobConfigurable

Initializes a new instance from a JobConf.

Specified by:

configure in interface JobConfigurable

Parameters:

job - the configuration

getPartition

public int getPartition(K2 key,
                        V2 value,
                        int numReduceTasks)

Use Object.hashCode() to partition.

Specified by:

getPartition in interface Partitioner<K2,V2>

Parameters:

key - the key to be paritioned.

value - the entry value.

numReduceTasks - the total number of partitions.

Returns:

the partition number for the key.