| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <!-- NewPage --> |
| <html lang="en"> |
| <head> |
| <!-- Generated by javadoc (1.8.0_292) on Tue Jun 15 06:00:55 GMT 2021 --> |
| <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> |
| <title>Partitioner (Apache Hadoop Main 3.3.1 API)</title> |
| <meta name="date" content="2021-06-15"> |
| <link rel="stylesheet" type="text/css" href="../../../../stylesheet.css" title="Style"> |
| <script type="text/javascript" src="../../../../script.js"></script> |
| </head> |
| <body> |
| <script type="text/javascript"><!-- |
| try { |
| if (location.href.indexOf('is-external=true') == -1) { |
| parent.document.title="Partitioner (Apache Hadoop Main 3.3.1 API)"; |
| } |
| } |
| catch(err) { |
| } |
| //--> |
| var methods = {"i0":6}; |
| var tabs = {65535:["t0","All Methods"],2:["t2","Instance Methods"],4:["t3","Abstract Methods"]}; |
| var altColor = "altColor"; |
| var rowColor = "rowColor"; |
| var tableTab = "tableTab"; |
| var activeTableTab = "activeTableTab"; |
| </script> |
| <noscript> |
| <div>JavaScript is disabled on your browser.</div> |
| </noscript> |
| <!-- ========= START OF TOP NAVBAR ======= --> |
| <div class="topNav"><a name="navbar.top"> |
| <!-- --> |
| </a> |
| <div class="skipNav"><a href="#skip.navbar.top" title="Skip navigation links">Skip navigation links</a></div> |
| <a name="navbar.top.firstrow"> |
| <!-- --> |
| </a> |
| <ul class="navList" title="Navigation"> |
| <li><a href="../../../../overview-summary.html">Overview</a></li> |
| <li><a href="package-summary.html">Package</a></li> |
| <li class="navBarCell1Rev">Class</li> |
| <li><a href="class-use/Partitioner.html">Use</a></li> |
| <li><a href="package-tree.html">Tree</a></li> |
| <li><a href="../../../../deprecated-list.html">Deprecated</a></li> |
| <li><a href="../../../../index-all.html">Index</a></li> |
| <li><a href="../../../../help-doc.html">Help</a></li> |
| </ul> |
| </div> |
| <div class="subNav"> |
| <ul class="navList"> |
| <li><a href="../../../../org/apache/hadoop/mapred/OutputLogFilter.html" title="class in org.apache.hadoop.mapred"><span class="typeNameLink">Prev Class</span></a></li> |
| <li><a href="../../../../org/apache/hadoop/mapred/RecordReader.html" title="interface in org.apache.hadoop.mapred"><span class="typeNameLink">Next Class</span></a></li> |
| </ul> |
| <ul class="navList"> |
| <li><a href="../../../../index.html?org/apache/hadoop/mapred/Partitioner.html" target="_top">Frames</a></li> |
| <li><a href="Partitioner.html" target="_top">No Frames</a></li> |
| </ul> |
| <ul class="navList" id="allclasses_navbar_top"> |
| <li><a href="../../../../allclasses-noframe.html">All Classes</a></li> |
| </ul> |
| <div> |
| <script type="text/javascript"><!-- |
| allClassesLink = document.getElementById("allclasses_navbar_top"); |
| if(window==top) { |
| allClassesLink.style.display = "block"; |
| } |
| else { |
| allClassesLink.style.display = "none"; |
| } |
| //--> |
| </script> |
| </div> |
| <div> |
| <ul class="subNavList"> |
| <li>Summary: </li> |
| <li>Nested | </li> |
| <li>Field | </li> |
| <li>Constr | </li> |
| <li><a href="#method.summary">Method</a></li> |
| </ul> |
| <ul class="subNavList"> |
| <li>Detail: </li> |
| <li>Field | </li> |
| <li>Constr | </li> |
| <li><a href="#method.detail">Method</a></li> |
| </ul> |
| </div> |
| <a name="skip.navbar.top"> |
| <!-- --> |
| </a></div> |
| <!-- ========= END OF TOP NAVBAR ========= --> |
| <!-- ======== START OF CLASS DATA ======== --> |
| <div class="header"> |
| <div class="subTitle">org.apache.hadoop.mapred</div> |
| <h2 title="Interface Partitioner" class="title">Interface Partitioner<K2,V2></h2> |
| </div> |
| <div class="contentContainer"> |
| <div class="description"> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <dl> |
| <dt>All Superinterfaces:</dt> |
| <dd><a href="../../../../org/apache/hadoop/mapred/JobConfigurable.html" title="interface in org.apache.hadoop.mapred">JobConfigurable</a></dd> |
| </dl> |
| <dl> |
| <dt>All Known Implementing Classes:</dt> |
| <dd><a href="../../../../org/apache/hadoop/mapred/lib/BinaryPartitioner.html" title="class in org.apache.hadoop.mapred.lib">BinaryPartitioner</a>, <a href="../../../../org/apache/hadoop/mapred/lib/HashPartitioner.html" title="class in org.apache.hadoop.mapred.lib">HashPartitioner</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/mapred/lib/TotalOrderPartitioner.html" title="class in org.apache.hadoop.mapred.lib">TotalOrderPartitioner</a></dd> |
| </dl> |
| <hr> |
| <br> |
| <pre>@InterfaceAudience.Public |
| @InterfaceStability.Stable |
| public interface <span class="typeNameLabel">Partitioner<K2,V2></span> |
| extends <a href="../../../../org/apache/hadoop/mapred/JobConfigurable.html" title="interface in org.apache.hadoop.mapred">JobConfigurable</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></div> |
| <dl> |
| <dt><span class="seeLabel">See Also:</span></dt> |
| <dd><a href="../../../../org/apache/hadoop/mapred/Reducer.html" title="interface in org.apache.hadoop.mapred"><code>Reducer</code></a></dd> |
| </dl> |
| </li> |
| </ul> |
| </div> |
| <div class="summary"> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <!-- ========== METHOD SUMMARY =========== --> |
| <ul class="blockList"> |
| <li class="blockList"><a name="method.summary"> |
| <!-- --> |
| </a> |
| <h3>Method Summary</h3> |
| <table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Method Summary table, listing methods, and an explanation"> |
| <caption><span id="t0" class="activeTableTab"><span>All Methods</span><span class="tabEnd"> </span></span><span id="t2" class="tableTab"><span><a href="javascript:show(2);">Instance Methods</a></span><span class="tabEnd"> </span></span><span id="t3" class="tableTab"><span><a href="javascript:show(4);">Abstract Methods</a></span><span class="tabEnd"> </span></span></caption> |
| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colLast" scope="col">Method and Description</th> |
| </tr> |
| <tr id="i0" class="altColor"> |
| <td class="colFirst"><code>int</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../org/apache/hadoop/mapred/Partitioner.html#getPartition-K2-V2-int-">getPartition</a></span>(<a href="../../../../org/apache/hadoop/mapred/Partitioner.html" title="type parameter in Partitioner">K2</a> key, |
| <a href="../../../../org/apache/hadoop/mapred/Partitioner.html" title="type parameter in Partitioner">V2</a> value, |
| int numPartitions)</code> |
| <div class="block">Get the paritition number for a given key (hence record) given the total |
| number of partitions i.e.</div> |
| </td> |
| </tr> |
| </table> |
| <ul class="blockList"> |
| <li class="blockList"><a name="methods.inherited.from.class.org.apache.hadoop.mapred.JobConfigurable"> |
| <!-- --> |
| </a> |
| <h3>Methods inherited from interface org.apache.hadoop.mapred.<a href="../../../../org/apache/hadoop/mapred/JobConfigurable.html" title="interface in org.apache.hadoop.mapred">JobConfigurable</a></h3> |
| <code><a href="../../../../org/apache/hadoop/mapred/JobConfigurable.html#configure-org.apache.hadoop.mapred.JobConf-">configure</a></code></li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </div> |
| <div class="details"> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <!-- ============ METHOD DETAIL ========== --> |
| <ul class="blockList"> |
| <li class="blockList"><a name="method.detail"> |
| <!-- --> |
| </a> |
| <h3>Method Detail</h3> |
| <a name="getPartition-java.lang.Object-java.lang.Object-int-"> |
| <!-- --> |
| </a><a name="getPartition-K2-V2-int-"> |
| <!-- --> |
| </a> |
| <ul class="blockListLast"> |
| <li class="blockList"> |
| <h4>getPartition</h4> |
| <pre>int getPartition(<a href="../../../../org/apache/hadoop/mapred/Partitioner.html" title="type parameter in Partitioner">K2</a> key, |
| <a href="../../../../org/apache/hadoop/mapred/Partitioner.html" title="type parameter in Partitioner">V2</a> value, |
| int numPartitions)</pre> |
| <div class="block">Get the paritition 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 paritioned.</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> |
| </dl> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </div> |
| </div> |
| <!-- ========= END OF CLASS DATA ========= --> |
| <!-- ======= START OF BOTTOM NAVBAR ====== --> |
| <div class="bottomNav"><a name="navbar.bottom"> |
| <!-- --> |
| </a> |
| <div class="skipNav"><a href="#skip.navbar.bottom" title="Skip navigation links">Skip navigation links</a></div> |
| <a name="navbar.bottom.firstrow"> |
| <!-- --> |
| </a> |
| <ul class="navList" title="Navigation"> |
| <li><a href="../../../../overview-summary.html">Overview</a></li> |
| <li><a href="package-summary.html">Package</a></li> |
| <li class="navBarCell1Rev">Class</li> |
| <li><a href="class-use/Partitioner.html">Use</a></li> |
| <li><a href="package-tree.html">Tree</a></li> |
| <li><a href="../../../../deprecated-list.html">Deprecated</a></li> |
| <li><a href="../../../../index-all.html">Index</a></li> |
| <li><a href="../../../../help-doc.html">Help</a></li> |
| </ul> |
| </div> |
| <div class="subNav"> |
| <ul class="navList"> |
| <li><a href="../../../../org/apache/hadoop/mapred/OutputLogFilter.html" title="class in org.apache.hadoop.mapred"><span class="typeNameLink">Prev Class</span></a></li> |
| <li><a href="../../../../org/apache/hadoop/mapred/RecordReader.html" title="interface in org.apache.hadoop.mapred"><span class="typeNameLink">Next Class</span></a></li> |
| </ul> |
| <ul class="navList"> |
| <li><a href="../../../../index.html?org/apache/hadoop/mapred/Partitioner.html" target="_top">Frames</a></li> |
| <li><a href="Partitioner.html" target="_top">No Frames</a></li> |
| </ul> |
| <ul class="navList" id="allclasses_navbar_bottom"> |
| <li><a href="../../../../allclasses-noframe.html">All Classes</a></li> |
| </ul> |
| <div> |
| <script type="text/javascript"><!-- |
| allClassesLink = document.getElementById("allclasses_navbar_bottom"); |
| if(window==top) { |
| allClassesLink.style.display = "block"; |
| } |
| else { |
| allClassesLink.style.display = "none"; |
| } |
| //--> |
| </script> |
| </div> |
| <div> |
| <ul class="subNavList"> |
| <li>Summary: </li> |
| <li>Nested | </li> |
| <li>Field | </li> |
| <li>Constr | </li> |
| <li><a href="#method.summary">Method</a></li> |
| </ul> |
| <ul class="subNavList"> |
| <li>Detail: </li> |
| <li>Field | </li> |
| <li>Constr | </li> |
| <li><a href="#method.detail">Method</a></li> |
| </ul> |
| </div> |
| <a name="skip.navbar.bottom"> |
| <!-- --> |
| </a></div> |
| <!-- ======== END OF BOTTOM NAVBAR ======= --> |
| <p class="legalCopy"><small>Copyright © 2021 <a href="https://www.apache.org">Apache Software Foundation</a>. All rights reserved.</small></p> |
| </body> |
| </html> |
