org.apache.hadoop.mapred.lib

Class IdentityReducer<K,V>

java.lang.Object

org.apache.hadoop.mapred.MapReduceBase

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

All Implemented Interfaces:

Closeable, AutoCloseable, JobConfigurable, Reducer<K,V,K,V>

@InterfaceAudience.Public
 @InterfaceStability.Stable
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

Constructors

Constructor and Description
IdentityReducer()

Method Summary

Modifier and Type	Method and Description
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