HashPartitioner (Hadoop 1.2.1 API) (original) (raw)

org.apache.hadoop.mapred.lib

Class HashPartitioner<K2,V2>

java.lang.Object extended by 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](../../../../../org/apache/hadoop/mapred/lib/HashPartitioner.html#getPartition%28K2, V2, int%29)(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](../../../../../org/apache/hadoop/mapred/JobConfigurable.html#configure%28org.apache.hadoop.mapred.JobConf%29)

Initializes a new instance from a JobConf.

Specified by:

[configure](../../../../../org/apache/hadoop/mapred/JobConfigurable.html#configure%28org.apache.hadoop.mapred.JobConf%29) in interface [JobConfigurable](../../../../../org/apache/hadoop/mapred/JobConfigurable.html "interface in org.apache.hadoop.mapred")

Parameters:

job - the configuration

getPartition

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

Use Object.hashCode() to partition.

Specified by:

[getPartition](../../../../../org/apache/hadoop/mapred/Partitioner.html#getPartition%28K2, V2, int%29) in interface [Partitioner](../../../../../org/apache/hadoop/mapred/Partitioner.html "interface in org.apache.hadoop.mapred")<[K2](../../../../../org/apache/hadoop/mapred/lib/HashPartitioner.html "type parameter in HashPartitioner"),[V2](../../../../../org/apache/hadoop/mapred/lib/HashPartitioner.html "type parameter in HashPartitioner")>

Parameters:

key - the key to be paritioned.

value - the entry value.

numReduceTasks - the total number of partitions.

Returns:

the partition number for the key.