org.apache.hadoop.mapred.lib
Class IdentityReducer<K,V>

java.lang.Object
  extended by org.apache.hadoop.mapred.MapReduceBase
      extended by org.apache.hadoop.mapred.lib.IdentityReducer<K,V>
All Implemented Interfaces:
Closeable, JobConfigurable, Reducer<K,V,K,V>

public class IdentityReducer<K,V>
extends MapReduceBase
implements Reducer<K,V,K,V>

Performs no reduction, writing all input values directly to the output.


Constructor Summary
IdentityReducer()
           
 
Method Summary
 void reduce(K key, Iterator<V> values, OutputCollector<K,V> output, Reporter reporter)
          Writes all keys and values directly to output.
 
Methods inherited from class org.apache.hadoop.mapred.MapReduceBase
close, configure
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface org.apache.hadoop.mapred.JobConfigurable
configure
 
Methods inherited from interface java.io.Closeable
close
 

Constructor Detail

IdentityReducer

public IdentityReducer()
Method Detail

reduce

public void reduce(K key,
                   Iterator<V> values,
                   OutputCollector<K,V> output,
                   Reporter reporter)
            throws IOException
Writes all keys and values directly to output.

Specified by:
reduce in interface Reducer<K,V,K,V>
Parameters:
key - the key.
values - the list of values to reduce.
output - to collect keys and combined values.
reporter - facility to report progress.
Throws:
IOException


Copyright © 2009 The Apache Software Foundation