org.apache.hadoop.mapred
Interface Partitioner

All Superinterfaces:

JobConfigurable

All Known Implementing Classes:

HashPartitioner, KeyFieldBasedPartitioner

public interface Partitioner
extends JobConfigurable

Partitions the key space. A partition is created for each reduce task.

Method Summary

int	getPartition(WritableComparable key, Writable value, int numPartitions) Returns the paritition number for a given entry given the total number of partitions.

Methods inherited from interface org.apache.hadoop.mapred.JobConfigurable

configure

Method Detail

getPartition

int getPartition(WritableComparable key,
                 Writable value,
                 int numPartitions)

Returns the paritition number for a given entry given the total number of partitions. Typically a hash function on a all or a subset of the key.

Parameters:

key - the entry key

value - the entry value

numPartitions - the number of partitions

Returns:

the partition number