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 <h2 title="Class Partitioner" class="title">Class Partitioner&lt;KEY,VALUE&gt;</h2>
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 <pre>@InterfaceAudience.Public
  @InterfaceStability.Stable
 public abstract class <span class="typeNameLabel">Partitioner&lt;KEY,VALUE&gt;</span>
 extends <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</a></pre>
 <div class="block">Partitions the key space.

  <p><code>Partitioner</code> controls the partitioning of the keys of the
  intermediate map-outputs. The key (or a subset of the key) is used to derive
  the partition, typically by a hash function. The total number of partitions
  is the same as the number of reduce tasks for the job. Hence this controls
  which of the <code>m</code> reduce tasks the intermediate key (and hence the
  record) is sent for reduction.</p>

  <p>Note: A <code>Partitioner</code> is created only when there are multiple
  reducers.</p>

  <p>Note: If you require your Partitioner class to obtain the Job's
  configuration object, implement the <a href="../../../../org/apache/hadoop/conf/Configurable.html" title="interface in org.apache.hadoop.conf"><code>Configurable</code></a> interface.</p></div>
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 <dd><a href="../../../../org/apache/hadoop/mapreduce/Reducer.html" title="class in org.apache.hadoop.mapreduce"><code>Reducer</code></a></dd>
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 <td class="colFirst"><code>abstract int</code></td>
 <td class="colLast"><code><span class="memberNameLink"><a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html#getPartition-KEY-VALUE-int-">getPartition</a></span>(<a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="type parameter in Partitioner">KEY</a>&nbsp;key,
             <a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="type parameter in Partitioner">VALUE</a>&nbsp;value,
             int&nbsp;numPartitions)</code>
 <div class="block">Get the partition number for a given key (hence record) given the total
  number of partitions i.e.</div>
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 <pre>public&nbsp;Partitioner()</pre>
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 <pre>public abstract&nbsp;int&nbsp;getPartition(<a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="type parameter in Partitioner">KEY</a>&nbsp;key,
                                  <a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="type parameter in Partitioner">VALUE</a>&nbsp;value,
                                  int&nbsp;numPartitions)</pre>
 <div class="block">Get the partition number for a given key (hence record) given the total
  number of partitions i.e. number of reduce-tasks for the job.

  <p>Typically a hash function on a all or a subset of the key.</p></div>
 <dl>
 <dt><span class="paramLabel">Parameters:</span></dt>
 <dd><code>key</code> - the key to be partioned.</dd>
 <dd><code>value</code> - the entry value.</dd>
 <dd><code>numPartitions</code> - the total number of partitions.</dd>
 <dt><span class="returnLabel">Returns:</span></dt>
 <dd>the partition number for the <code>key</code>.</dd>
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	<h2 title="Class Partitioner" class="title">Class Partitioner<KEY,VALUE></h2>
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	<pre>@InterfaceAudience.Public
	@InterfaceStability.Stable
	public abstract class <span class="typeNameLabel">Partitioner<KEY,VALUE></span>
	extends <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</a></pre>
	<div class="block">Partitions the key space.

	<p><code>Partitioner</code> controls the partitioning of the keys of the
	intermediate map-outputs. The key (or a subset of the key) is used to derive
	the partition, typically by a hash function. The total number of partitions
	is the same as the number of reduce tasks for the job. Hence this controls
	which of the <code>m</code> reduce tasks the intermediate key (and hence the
	record) is sent for reduction.</p>

	<p>Note: A <code>Partitioner</code> is created only when there are multiple
	reducers.</p>

	<p>Note: If you require your Partitioner class to obtain the Job's
	configuration object, implement the <a href="../../../../org/apache/hadoop/conf/Configurable.html" title="interface in org.apache.hadoop.conf"><code>Configurable</code></a> interface.</p></div>
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	<dd><a href="../../../../org/apache/hadoop/mapreduce/Reducer.html" title="class in org.apache.hadoop.mapreduce"><code>Reducer</code></a></dd>
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	<td class="colFirst"><code>abstract int</code></td>
	<td class="colLast"><code><span class="memberNameLink"><a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html#getPartition-KEY-VALUE-int-">getPartition</a></span>(<a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="type parameter in Partitioner">KEY</a> key,
	<a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="type parameter in Partitioner">VALUE</a> value,
	int numPartitions)</code>
	<div class="block">Get the partition number for a given key (hence record) given the total
	number of partitions i.e.</div>
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	<h4>Partitioner</h4>
	<pre>public Partitioner()</pre>
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	<h4>getPartition</h4>
	<pre>public abstract int getPartition(<a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="type parameter in Partitioner">KEY</a> key,
	<a href="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="type parameter in Partitioner">VALUE</a> value,
	int numPartitions)</pre>
	<div class="block">Get the partition number for a given key (hence record) given the total
	number of partitions i.e. number of reduce-tasks for the job.

	<p>Typically a hash function on a all or a subset of the key.</p></div>
	<dl>
	<dt><span class="paramLabel">Parameters:</span></dt>
	<dd><code>key</code> - the key to be partioned.</dd>
	<dd><code>value</code> - the entry value.</dd>
	<dd><code>numPartitions</code> - the total number of partitions.</dd>
	<dt><span class="returnLabel">Returns:</span></dt>
	<dd>the partition number for the <code>key</code>.</dd>
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