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7ValueAggregatorDescriptor (Hadoop 0.20.1 API)
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90<FONT SIZE="-1">
91org.apache.hadoop.mapred.lib.aggregate</FONT>
92<BR>
93Interface ValueAggregatorDescriptor</H2>
94<DL>
95<DT><B>All Known Implementing Classes:</B> <DD><A HREF="../../../../../../org/apache/hadoop/examples/AggregateWordCount.WordCountPlugInClass.html" title="class in org.apache.hadoop.examples">AggregateWordCount.WordCountPlugInClass</A>, <A HREF="../../../../../../org/apache/hadoop/examples/AggregateWordHistogram.AggregateWordHistogramPlugin.html" title="class in org.apache.hadoop.examples">AggregateWordHistogram.AggregateWordHistogramPlugin</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/mapred/lib/aggregate/ValueAggregatorBaseDescriptor.html" title="class in org.apache.hadoop.mapred.lib.aggregate">ValueAggregatorBaseDescriptor</A></DD>
96</DL>
97<HR>
98<DL>
99<DT><PRE>public interface <B>ValueAggregatorDescriptor</B></DL>
100</PRE>
101
102<P>
103This interface defines the contract a value aggregator descriptor must
104 support. Such a descriptor can be configured with a JobConf object. Its main
105 function is to generate a list of aggregation-id/value pairs. An aggregation
106 id encodes an aggregation type which is used to guide the way to aggregate
107 the value in the reduce/combiner phrase of an Aggregate based job.The mapper in
108 an Aggregate based map/reduce job may create one or more of
109 ValueAggregatorDescriptor objects at configuration time. For each input
110 key/value pair, the mapper will use those objects to create aggregation
111 id/value pairs.
112<P>
113
114<P>
115<HR>
116
117<P>
118<!-- =========== FIELD SUMMARY =========== -->
119
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123<TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2">
124<B>Field Summary</B></FONT></TH>
125</TR>
126<TR BGCOLOR="white" CLASS="TableRowColor">
127<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
128<CODE>static&nbsp;<A HREF="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</A></CODE></FONT></TD>
129<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapred/lib/aggregate/ValueAggregatorDescriptor.html#ONE">ONE</A></B></CODE>
130
131<BR>
132&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</TD>
133</TR>
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135<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
136<CODE>static&nbsp;<A HREF="http://java.sun.com/javase/6/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A></CODE></FONT></TD>
137<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapred/lib/aggregate/ValueAggregatorDescriptor.html#TYPE_SEPARATOR">TYPE_SEPARATOR</A></B></CODE>
138
139<BR>
140&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</TD>
141</TR>
142</TABLE>
143&nbsp;
144<!-- ========== METHOD SUMMARY =========== -->
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149<TH ALIGN="left" COLSPAN="2"><FONT SIZE="+2">
150<B>Method Summary</B></FONT></TH>
151</TR>
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153<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
154<CODE>&nbsp;void</CODE></FONT></TD>
155<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapred/lib/aggregate/ValueAggregatorDescriptor.html#configure(org.apache.hadoop.mapred.JobConf)">configure</A></B>(<A HREF="../../../../../../org/apache/hadoop/mapred/JobConf.html" title="class in org.apache.hadoop.mapred">JobConf</A>&nbsp;job)</CODE>
156
157<BR>
158&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Configure the object</TD>
159</TR>
160<TR BGCOLOR="white" CLASS="TableRowColor">
161<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
162<CODE>&nbsp;<A HREF="http://java.sun.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://java.sun.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>
163<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapred/lib/aggregate/ValueAggregatorDescriptor.html#generateKeyValPairs(java.lang.Object, java.lang.Object)">generateKeyValPairs</A></B>(<A HREF="http://java.sun.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A>&nbsp;key,
164                    <A HREF="http://java.sun.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A>&nbsp;val)</CODE>
165
166<BR>
167&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>
168</TR>
169</TABLE>
170&nbsp;
171<P>
172
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182
183<A NAME="TYPE_SEPARATOR"><!-- --></A><H3>
184TYPE_SEPARATOR</H3>
185<PRE>
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187<DL>
188<DL>
189<DT><B>See Also:</B><DD><A HREF="../../../../../../constant-values.html#org.apache.hadoop.mapred.lib.aggregate.ValueAggregatorDescriptor.TYPE_SEPARATOR">Constant Field Values</A></DL>
190</DL>
191<HR>
192
193<A NAME="ONE"><!-- --></A><H3>
194ONE</H3>
195<PRE>
196static final <A HREF="../../../../../../org/apache/hadoop/io/Text.html" title="class in org.apache.hadoop.io">Text</A> <B>ONE</B></PRE>
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208<B>Method Detail</B></FONT></TH>
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210</TABLE>
211
212<A NAME="generateKeyValPairs(java.lang.Object, java.lang.Object)"><!-- --></A><H3>
213generateKeyValPairs</H3>
214<PRE>
215<A HREF="http://java.sun.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://java.sun.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; <B>generateKeyValPairs</B>(<A HREF="http://java.sun.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A>&nbsp;key,
216                                                    <A HREF="http://java.sun.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A>&nbsp;val)</PRE>
217<DL>
218<DD>Generate a list of aggregation-id/value pairs for the given key/value pair.
219 This function is usually called by the mapper of an Aggregate based job.
220<P>
221<DD><DL>
222<DT><B>Parameters:</B><DD><CODE>key</CODE> - input key<DD><CODE>val</CODE> - input value
223<DT><B>Returns:</B><DD>a list of aggregation id/value pairs. An aggregation id encodes an
224         aggregation type which is used to guide the way to aggregate the
225         value in the reduce/combiner phrase of an Aggregate based job.</DL>
226</DD>
227</DL>
228<HR>
229
230<A NAME="configure(org.apache.hadoop.mapred.JobConf)"><!-- --></A><H3>
231configure</H3>
232<PRE>
233void <B>configure</B>(<A HREF="../../../../../../org/apache/hadoop/mapred/JobConf.html" title="class in org.apache.hadoop.mapred">JobConf</A>&nbsp;job)</PRE>
234<DL>
235<DD>Configure the object
236<P>
237<DD><DL>
238<DT><B>Parameters:</B><DD><CODE>job</CODE> - a JobConf object that may contain the information that can be used
239          to configure the object.</DL>
240</DD>
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