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| <div class="subTitle">org.apache.hadoop.mapreduce.lib.partition</div> |
| <h2 title="Class RehashPartitioner" class="title">Class RehashPartitioner<K,V></h2> |
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| <li><a href="../../../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="class in org.apache.hadoop.mapreduce">org.apache.hadoop.mapreduce.Partitioner</a><K,V></li> |
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| <li>org.apache.hadoop.mapreduce.lib.partition.RehashPartitioner<K,V></li> |
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| <pre>@InterfaceAudience.Public |
| @InterfaceStability.Stable |
| public class <span class="typeNameLabel">RehashPartitioner<K,V></span> |
| extends <a href="../../../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="class in org.apache.hadoop.mapreduce">Partitioner</a><K,V></pre> |
| <div class="block">This partitioner rehashes values returned by <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html?is-external=true#hashCode--" title="class or interface in java.lang"><code>Object.hashCode()</code></a> |
| to get smoother distribution between partitions which may improve |
| reduce reduce time in some cases and should harm things in no cases. |
| This partitioner is suggested with Integer and Long keys with simple |
| patterns in their distributions.</div> |
| <dl> |
| <dt><span class="simpleTagLabel">Since:</span></dt> |
| <dd>2.0.3</dd> |
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| <td class="colOne"><code><span class="memberNameLink"><a href="../../../../../../org/apache/hadoop/mapreduce/lib/partition/RehashPartitioner.html#RehashPartitioner--">RehashPartitioner</a></span>()</code> </td> |
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| <td class="colFirst"><code>int</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/hadoop/mapreduce/lib/partition/RehashPartitioner.html#getPartition-K-V-int-">getPartition</a></span>(<a href="../../../../../../org/apache/hadoop/mapreduce/lib/partition/RehashPartitioner.html" title="type parameter in RehashPartitioner">K</a> key, |
| <a href="../../../../../../org/apache/hadoop/mapreduce/lib/partition/RehashPartitioner.html" title="type parameter in RehashPartitioner">V</a> value, |
| int numReduceTasks)</code> |
| <div class="block">Rehash <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html?is-external=true#hashCode--" title="class or interface in java.lang"><code>Object.hashCode()</code></a> to partition.</div> |
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| <h4>RehashPartitioner</h4> |
| <pre>public RehashPartitioner()</pre> |
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| <h4>getPartition</h4> |
| <pre>public int getPartition(<a href="../../../../../../org/apache/hadoop/mapreduce/lib/partition/RehashPartitioner.html" title="type parameter in RehashPartitioner">K</a> key, |
| <a href="../../../../../../org/apache/hadoop/mapreduce/lib/partition/RehashPartitioner.html" title="type parameter in RehashPartitioner">V</a> value, |
| int numReduceTasks)</pre> |
| <div class="block">Rehash <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html?is-external=true#hashCode--" title="class or interface in java.lang"><code>Object.hashCode()</code></a> to partition.</div> |
| <dl> |
| <dt><span class="overrideSpecifyLabel">Specified by:</span></dt> |
| <dd><code><a href="../../../../../../org/apache/hadoop/mapreduce/Partitioner.html#getPartition-KEY-VALUE-int-">getPartition</a></code> in class <code><a href="../../../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="class in org.apache.hadoop.mapreduce">Partitioner</a><<a href="../../../../../../org/apache/hadoop/mapreduce/lib/partition/RehashPartitioner.html" title="type parameter in RehashPartitioner">K</a>,<a href="../../../../../../org/apache/hadoop/mapreduce/lib/partition/RehashPartitioner.html" title="type parameter in RehashPartitioner">V</a>></code></dd> |
| <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>numReduceTasks</code> - the total number of partitions.</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>the partition number for the <code>key</code>.</dd> |
| </dl> |
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