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7Partitioner (Hadoop 0.20.1 API)
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91org.apache.hadoop.mapred</FONT>
92<BR>
93Interface Partitioner&lt;K2,V2&gt;</H2>
94<DL>
95<DT><B>All Superinterfaces:</B> <DD><A HREF="../../../../org/apache/hadoop/mapred/JobConfigurable.html" title="interface in org.apache.hadoop.mapred">JobConfigurable</A></DD>
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98<DT><B>All Known Implementing Classes:</B> <DD><A HREF="../../../../org/apache/hadoop/mapred/lib/HashPartitioner.html" title="class in org.apache.hadoop.mapred.lib">HashPartitioner</A>, <A HREF="../../../../org/apache/hadoop/contrib/index/mapred/IndexUpdatePartitioner.html" title="class in org.apache.hadoop.contrib.index.mapred">IndexUpdatePartitioner</A>, <A HREF="../../../../org/apache/hadoop/mapred/lib/KeyFieldBasedPartitioner.html" title="class in org.apache.hadoop.mapred.lib">KeyFieldBasedPartitioner</A>, <A HREF="../../../../org/apache/hadoop/examples/SleepJob.html" title="class in org.apache.hadoop.examples">SleepJob</A>, <A HREF="../../../../org/apache/hadoop/mapred/lib/TotalOrderPartitioner.html" title="class in org.apache.hadoop.mapred.lib">TotalOrderPartitioner</A></DD>
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101<B>Deprecated.</B>&nbsp;<I>Use <A HREF="../../../../org/apache/hadoop/mapreduce/Partitioner.html" title="class in org.apache.hadoop.mapreduce"><CODE>Partitioner</CODE></A> instead.</I>
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105</FONT>public interface <B>Partitioner&lt;K2,V2&gt;</B><DT>extends <A HREF="../../../../org/apache/hadoop/mapred/JobConfigurable.html" title="interface in org.apache.hadoop.mapred">JobConfigurable</A></DL>
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107
108<P>
109Partitions the key space.
110 
111 <p><code>Partitioner</code> controls the partitioning of the keys of the
112 intermediate map-outputs. The key (or a subset of the key) is used to derive
113 the partition, typically by a hash function. The total number of partitions
114 is the same as the number of reduce tasks for the job. Hence this controls
115 which of the <code>m</code> reduce tasks the intermediate key (and hence the
116 record) is sent for reduction.</p>
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118
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136<CODE>&nbsp;int</CODE></FONT></TD>
137<TD><CODE><B><A HREF="../../../../org/apache/hadoop/mapred/Partitioner.html#getPartition(K2, V2, int)">getPartition</A></B>(<A HREF="../../../../org/apache/hadoop/mapred/Partitioner.html" title="type parameter in Partitioner">K2</A>&nbsp;key,
138             <A HREF="../../../../org/apache/hadoop/mapred/Partitioner.html" title="type parameter in Partitioner">V2</A>&nbsp;value,
139             int&nbsp;numPartitions)</CODE>
140
141<BR>
142&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Deprecated.</B>&nbsp;Get the paritition number for a given key (hence record) given the total
143 number of partitions i.e.</TD>
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168<A NAME="getPartition(java.lang.Object,java.lang.Object,int)"><!-- --></A><A NAME="getPartition(K2, V2, int)"><!-- --></A><H3>
169getPartition</H3>
170<PRE>
171int <B>getPartition</B>(<A HREF="../../../../org/apache/hadoop/mapred/Partitioner.html" title="type parameter in Partitioner">K2</A>&nbsp;key,
172                 <A HREF="../../../../org/apache/hadoop/mapred/Partitioner.html" title="type parameter in Partitioner">V2</A>&nbsp;value,
173                 int&nbsp;numPartitions)</PRE>
174<DL>
175<DD><B>Deprecated.</B>&nbsp;<DD>Get the paritition number for a given key (hence record) given the total
176 number of partitions i.e. number of reduce-tasks for the job.
177   
178 <p>Typically a hash function on a all or a subset of the key.</p>
179<P>
180<DD><DL>
181</DL>
182</DD>
183<DD><DL>
184<DT><B>Parameters:</B><DD><CODE>key</CODE> - the key to be paritioned.<DD><CODE>value</CODE> - the entry value.<DD><CODE>numPartitions</CODE> - the total number of partitions.
185<DT><B>Returns:</B><DD>the partition number for the <code>key</code>.</DL>
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