hashpartitioner.java

hadoop:Nutch集群平台

/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.mapred.lib;

import org.apache.hadoop.mapred.Partitioner;
import org.apache.hadoop.mapred.JobConf;

import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.Writable;

/** Partition keys by their {@link Object#hashCode()}. */
public class HashPartitioner implements Partitioner {

  public void configure(JobConf job) {}

  /** Use {@link Object#hashCode()} to partition. */
  public int getPartition(WritableComparable key, Writable value,
                          int numReduceTasks) {
    return (key.hashCode() & Integer.MAX_VALUE) % numReduceTasks;
  }

}