com.bigdata.service.mapred
Interface IHashFunction

All Superinterfaces:

Serializable

All Known Implementing Classes:

DefaultHashFunction

public interface IHashFunction
extends Serializable

Interface for a hash function to be applied to the keys generated by an IMapTask. The hash function (modulo the #of reduce tasks) is used to assign the key-value pairs generated by an IMapTask to a reduce task.

Version:

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

Author:

Bryan Thompson

Method Summary

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

Method Detail

hashCode

int hashCode(byte[] key)

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.

Parameters:

key - The key produced by an IMapTask.

Returns:

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