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ValueAggregatorDescriptor (Apache Hadoop Main 2.0.0-alpha API)
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org.apache.hadoop.mapreduce.lib.aggregate</FONT>
<BR>
Interface ValueAggregatorDescriptor</H2>
<DL>
<DT><B>All Known Subinterfaces:</B> <DD><A HREF="../../../../../../org/apache/hadoop/mapred/lib/aggregate/ValueAggregatorDescriptor.html" title="interface in org.apache.hadoop.mapred.lib.aggregate">ValueAggregatorDescriptor</A></DD>
</DL>
<DL>
<DT><B>All Known Implementing Classes:</B> <DD><A HREF="../../../../../../org/apache/hadoop/mapreduce/lib/aggregate/UserDefinedValueAggregatorDescriptor.html" title="class in org.apache.hadoop.mapreduce.lib.aggregate">UserDefinedValueAggregatorDescriptor</A>, <A HREF="../../../../../../org/apache/hadoop/mapred/lib/aggregate/UserDefinedValueAggregatorDescriptor.html" title="class in org.apache.hadoop.mapred.lib.aggregate">UserDefinedValueAggregatorDescriptor</A>, <A HREF="../../../../../../org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorBaseDescriptor.html" title="class in org.apache.hadoop.mapreduce.lib.aggregate">ValueAggregatorBaseDescriptor</A>, <A HREF="../../../../../../org/apache/hadoop/mapred/lib/aggregate/ValueAggregatorBaseDescriptor.html" title="class in org.apache.hadoop.mapred.lib.aggregate">ValueAggregatorBaseDescriptor</A></DD>
</DL>
<HR>
<DL>
<DT><PRE><FONT SIZE="-1">@InterfaceAudience.Public
@InterfaceStability.Stable
</FONT>public interface <A HREF="../../../../../../src-html/org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#line.44"><B>ValueAggregatorDescriptor</B></A></DL>
</PRE>

<P>
This interface defines the contract a value aggregator descriptor must
 support. Such a descriptor can be configured with a <A HREF="../../../../../../org/apache/hadoop/conf/Configuration.html" title="class in org.apache.hadoop.conf"><CODE>Configuration</CODE></A>
 object. Its main function is to generate a list of aggregation-id/value 
 pairs. An aggregation id encodes an aggregation type which is used to 
 guide the way to aggregate the value in the reduce/combiner phrase of an
 Aggregate based job. 
 The mapper in an Aggregate based map/reduce job may create one or more of
 ValueAggregatorDescriptor objects at configuration time. For each input
 key/value pair, the mapper will use those objects to create aggregation
 id/value pairs.
<P>

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<!-- =========== FIELD SUMMARY =========== -->

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<B>Field Summary</B></FONT></TH>
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<CODE>static&nbsp;<A HREF="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#ONE">ONE</A></B></CODE>

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</TD>
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<CODE>static&nbsp;<A HREF="http://download.oracle.com/javase/6/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#TYPE_SEPARATOR">TYPE_SEPARATOR</A></B></CODE>

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<CODE>&nbsp;void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#configure(org.apache.hadoop.conf.Configuration)">configure</A></B>(<A HREF="../../../../../../org/apache/hadoop/conf/Configuration.html" title="class in org.apache.hadoop.conf">Configuration</A>&nbsp;conf)</CODE>

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Configure the object</TD>
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<CODE>&nbsp;<A HREF="http://download.oracle.com/javase/6/docs/api/java/util/ArrayList.html?is-external=true" title="class or interface in java.util">ArrayList</A>&lt;<A HREF="http://download.oracle.com/javase/6/docs/api/java/util/Map.Entry.html?is-external=true" title="class or interface in java.util">Map.Entry</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>&gt;&gt;</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#generateKeyValPairs(java.lang.Object, java.lang.Object)">generateKeyValPairs</A></B>(<A HREF="http://download.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A>&nbsp;key,
                                       <A HREF="http://download.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A>&nbsp;val)</CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Generate a list of aggregation-id/value pairs for 
 the given key/value pair.</TD>
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TYPE_SEPARATOR</H3>
<PRE>
static final <A HREF="http://download.oracle.com/javase/6/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A> <A HREF="../../../../../../src-html/org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#line.46"><B>TYPE_SEPARATOR</B></A></PRE>
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<DT><B>See Also:</B><DD><A HREF="../../../../../../constant-values.html#org.apache.hadoop.mapreduce.lib.aggregate.ValueAggregatorDescriptor.TYPE_SEPARATOR">Constant Field Values</A></DL>
</DL>
<HR>

<A NAME="ONE"><!-- --></A><H3>
ONE</H3>
<PRE>
static final <A HREF="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</A> <A HREF="../../../../../../src-html/org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#line.48"><B>ONE</B></A></PRE>
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<A NAME="generateKeyValPairs(java.lang.Object, java.lang.Object)"><!-- --></A><H3>
generateKeyValPairs</H3>
<PRE>
<A HREF="http://download.oracle.com/javase/6/docs/api/java/util/ArrayList.html?is-external=true" title="class or interface in java.util">ArrayList</A>&lt;<A HREF="http://download.oracle.com/javase/6/docs/api/java/util/Map.Entry.html?is-external=true" title="class or interface in java.util">Map.Entry</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>&gt;&gt; <A HREF="../../../../../../src-html/org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#line.63"><B>generateKeyValPairs</B></A>(<A HREF="http://download.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A>&nbsp;key,
                                                    <A HREF="http://download.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A>&nbsp;val)</PRE>
<DL>
<DD>Generate a list of aggregation-id/value pairs for 
 the given key/value pair.
 This function is usually called by the mapper of an Aggregate based job.
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>key</CODE> - input key<DD><CODE>val</CODE> - input value
<DT><B>Returns:</B><DD>a list of aggregation id/value pairs. An aggregation id encodes an
         aggregation type which is used to guide the way to aggregate the
         value in the reduce/combiner phrase of an Aggregate based job.</DL>
</DD>
</DL>
<HR>

<A NAME="configure(org.apache.hadoop.conf.Configuration)"><!-- --></A><H3>
configure</H3>
<PRE>
void <A HREF="../../../../../../src-html/org/apache/hadoop/mapreduce/lib/aggregate/ValueAggregatorDescriptor.html#line.73"><B>configure</B></A>(<A HREF="../../../../../../org/apache/hadoop/conf/Configuration.html" title="class in org.apache.hadoop.conf">Configuration</A>&nbsp;conf)</PRE>
<DL>
<DD>Configure the object
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>conf</CODE> - a Configuration object that may contain the information 
          that can be used to configure the object.</DL>
</DD>
</DL>
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