IdentityReducer (Hadoop 1.2.1 API)
Date: 2013-07-22

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## 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, 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`

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