IdentityReducer (Apache Hadoop Main 3.5.0 API)
Description: declaration: package: org.apache.hadoop.mapred.lib, class: IdentityReducer

Package 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`, `Closeable`, `JobConfigurable`, `Reducer<K,V,K,V>`

@Public @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
  Description
  `IdentityReducer()`

- ## Method Summary

  Modifier and Type
  Method
  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 java.io.Closeable

  `close`

  ### Methods inherited from interface org.apache.hadoop.mapred.JobConfigurable

  `configure`

- ## Constructor Details

  - ### IdentityReducer

    public IdentityReducer()

- ## Method Details

  - ### 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`