com.bigdata.service.mapred
Class DefaultHashFunction

java.lang.Object
  com.bigdata.service.mapred.DefaultHashFunction

All Implemented Interfaces:

IHashFunction, Serializable

public class DefaultHashFunction
extends Object
implements IHashFunction

This is default implementation of IHashFunction - it is based on Arrays.hashCode(byte[]).

Version:

$Id: DefaultHashFunction.java 2265 2009-10-26 12:51:06Z thompsonbry $

Author:

Bryan Thompson

See Also:

Serialized Form

Field Summary

static IHashFunction

INSTANCE

Method Summary

int	hashCode(byte[] key) The hash function used to assign map output keys to reduce tasks.

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final transient IHashFunction INSTANCE

Method Detail

hashCode

public int hashCode(byte[] key)

Description copied from interface: IHashFunction

The hash function used to assign map output keys to reduce tasks. This is normally hash(key) mod R, where hash(key) is Arrays.hashCode(byte[]) and R is the #of reduce tasks.

Specified by:

hashCode in interface IHashFunction

Parameters:

key - The key produced by an IMapTask.

Returns:

The index of the reduce service on which the key-value pair will be written.