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<div class="subTitle">org.apache.hadoop.mapreduce.lib.fieldsel</div>
<h2 title="Class FieldSelectionReducer" class="title">Class FieldSelectionReducer&lt;K,V&gt;</h2>
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<li><a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html" title="class in org.apache.hadoop.mapreduce">org.apache.hadoop.mapreduce.Reducer</a>&lt;<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>&gt;</li>
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<li>org.apache.hadoop.mapreduce.lib.fieldsel.FieldSelectionReducer&lt;K,V&gt;</li>
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<pre>@InterfaceAudience.Public
@InterfaceStability.Stable
public class <span class="typeNameLabel">FieldSelectionReducer&lt;K,V&gt;</span>
extends <a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html" title="class in org.apache.hadoop.mapreduce">Reducer</a>&lt;<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>&gt;</pre>
<div class="block">This class implements a reducer class that can be used to perform field
selections in a manner similar to unix cut.
The input data is treated as fields separated by a user specified
separator (the default value is "\t"). The user can specify a list of
fields that form the reduce output keys, and a list of fields that form
the reduce output values. The fields are the union of those from the key
and those from the value.
The field separator is under attribute "mapreduce.fieldsel.data.field.separator"
The reduce output field list spec is under attribute
"mapreduce.fieldsel.reduce.output.key.value.fields.spec".
The value is expected to be like
"keyFieldsSpec:valueFieldsSpec" key/valueFieldsSpec are comma (,)
separated field spec: fieldSpec,fieldSpec,fieldSpec ... Each field spec
can be a simple number (e.g. 5) specifying a specific field, or a range
(like 2-5) to specify a range of fields, or an open range (like 3-)
specifying all the fields starting from field 3. The open range field
spec applies value fields only. They have no effect on the key fields.
Here is an example: "4,3,0,1:6,5,1-3,7-". It specifies to use fields
4,3,0 and 1 for keys, and use fields 6,5,1,2,3,7 and above for values.</div>
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<h3>Field Summary</h3>
<table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Field Summary table, listing fields, and an explanation">
<caption><span>Fields</span><span class="tabEnd">&nbsp;</span></caption>
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<th class="colFirst" scope="col">Modifier and Type</th>
<th class="colLast" scope="col">Field and Description</th>
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<td class="colFirst"><code>static org.slf4j.Logger</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/hadoop/mapreduce/lib/fieldsel/FieldSelectionReducer.html#LOG">LOG</a></span></code>&nbsp;</td>
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<td class="colOne"><code><span class="memberNameLink"><a href="../../../../../../org/apache/hadoop/mapreduce/lib/fieldsel/FieldSelectionReducer.html#FieldSelectionReducer--">FieldSelectionReducer</a></span>()</code>&nbsp;</td>
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<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/hadoop/mapreduce/lib/fieldsel/FieldSelectionReducer.html#reduce-org.apache.hadoop.io.Text-java.lang.Iterable-org.apache.hadoop.mapreduce.Reducer.Context-">reduce</a></span>(<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>&nbsp;key,
<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Iterable.html?is-external=true" title="class or interface in java.lang">Iterable</a>&lt;<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>&gt;&nbsp;values,
org.apache.hadoop.mapreduce.Reducer.Context&nbsp;context)</code>
<div class="block">This method is called once for each key.</div>
</td>
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<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/hadoop/mapreduce/lib/fieldsel/FieldSelectionReducer.html#setup-org.apache.hadoop.mapreduce.Reducer.Context-">setup</a></span>(org.apache.hadoop.mapreduce.Reducer.Context&nbsp;context)</code>
<div class="block">Called once at the start of the task.</div>
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<h3>Methods inherited from class&nbsp;org.apache.hadoop.mapreduce.<a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html" title="class in org.apache.hadoop.mapreduce">Reducer</a></h3>
<code><a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html#cleanup-org.apache.hadoop.mapreduce.Reducer.Context-">cleanup</a>, <a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html#run-org.apache.hadoop.mapreduce.Reducer.Context-">run</a></code></li>
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<pre>public static final&nbsp;org.slf4j.Logger LOG</pre>
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<h4>FieldSelectionReducer</h4>
<pre>public&nbsp;FieldSelectionReducer()</pre>
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<h4>setup</h4>
<pre>public&nbsp;void&nbsp;setup(org.apache.hadoop.mapreduce.Reducer.Context&nbsp;context)
throws <a href="https://docs.oracle.com/javase/8/docs/api/java/io/IOException.html?is-external=true" title="class or interface in java.io">IOException</a>,
<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/InterruptedException.html?is-external=true" title="class or interface in java.lang">InterruptedException</a></pre>
<div class="block"><span class="descfrmTypeLabel">Description copied from class:&nbsp;<code><a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html#setup-org.apache.hadoop.mapreduce.Reducer.Context-">Reducer</a></code></span></div>
<div class="block">Called once at the start of the task.</div>
<dl>
<dt><span class="overrideSpecifyLabel">Overrides:</span></dt>
<dd><code><a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html#setup-org.apache.hadoop.mapreduce.Reducer.Context-">setup</a></code>&nbsp;in class&nbsp;<code><a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html" title="class in org.apache.hadoop.mapreduce">Reducer</a>&lt;<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>&gt;</code></dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="https://docs.oracle.com/javase/8/docs/api/java/io/IOException.html?is-external=true" title="class or interface in java.io">IOException</a></code></dd>
<dd><code><a href="https://docs.oracle.com/javase/8/docs/api/java/lang/InterruptedException.html?is-external=true" title="class or interface in java.lang">InterruptedException</a></code></dd>
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<h4>reduce</h4>
<pre>public&nbsp;void&nbsp;reduce(<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>&nbsp;key,
<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Iterable.html?is-external=true" title="class or interface in java.lang">Iterable</a>&lt;<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>&gt;&nbsp;values,
org.apache.hadoop.mapreduce.Reducer.Context&nbsp;context)
throws <a href="https://docs.oracle.com/javase/8/docs/api/java/io/IOException.html?is-external=true" title="class or interface in java.io">IOException</a>,
<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/InterruptedException.html?is-external=true" title="class or interface in java.lang">InterruptedException</a></pre>
<div class="block"><span class="descfrmTypeLabel">Description copied from class:&nbsp;<code><a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html#reduce-KEYIN-java.lang.Iterable-org.apache.hadoop.mapreduce.Reducer.Context-">Reducer</a></code></span></div>
<div class="block">This method is called once for each key. Most applications will define
their reduce class by overriding this method. The default implementation
is an identity function.</div>
<dl>
<dt><span class="overrideSpecifyLabel">Overrides:</span></dt>
<dd><code><a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html#reduce-KEYIN-java.lang.Iterable-org.apache.hadoop.mapreduce.Reducer.Context-">reduce</a></code>&nbsp;in class&nbsp;<code><a href="../../../../../../org/apache/hadoop/mapreduce/Reducer.html" title="class in org.apache.hadoop.mapreduce">Reducer</a>&lt;<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>,<a href="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</a>&gt;</code></dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="https://docs.oracle.com/javase/8/docs/api/java/io/IOException.html?is-external=true" title="class or interface in java.io">IOException</a></code></dd>
<dd><code><a href="https://docs.oracle.com/javase/8/docs/api/java/lang/InterruptedException.html?is-external=true" title="class or interface in java.lang">InterruptedException</a></code></dd>
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