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courses:mapreduce-tutorial:step-23 [2012/01/27 20:37]
straka 		courses:mapreduce-tutorial:step-23 [2012/01/31 12:20]
straka
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   * ''FloatWritable'' -- 64-bit floating number   * ''FloatWritable'' -- 64-bit floating number
   * ''DoubleWritable'' -- 64-bit floating number   * ''DoubleWritable'' -- 64-bit floating number
 +  * ''NullWritable'' -- no value
 For more complicated types like variable-length encoded integers, dictionaries, bloom filters, etc., see [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/io/Writable.html|Writable]]. For more complicated types like variable-length encoded integers, dictionaries, bloom filters, etc., see [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/io/Writable.html|Writable]].
 +
 +==== Types used in Perl API ====
 +The Perl API is always using strings as keys and values. From the Java point of view:
 +  * the type of keys and values produced by Perl API is always ''Text''.
 +  * any type can be used as input to Perl API -- if the type is different from ''Text'', a ''toString'' method is used to convert the value to string before the value is passed to Perl.
  
 ===== Input formats ===== ===== Input formats =====
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   * ''TextOutputFormat'': The type of both keys and values is ''Text''.   * ''TextOutputFormat'': The type of both keys and values is ''Text''.
   * ''SequenceFileOutputFormat'': Any type of keys and values can be used.   * ''SequenceFileOutputFormat'': Any type of keys and values can be used.
 +
 +----
 +
 +<html>
 +<table style="width:100%">
 +<tr>
 +<td style="text-align:left; width: 33%; "></html>[[step-22|Step 22]]: Optional – Setting Eclipse.<html></td>
 +<td style="text-align:center; width: 33%; "></html>[[.|Overview]]<html></td>
 +<td style="text-align:right; width: 33%; "></html>[[step-24|Step 24]]: Mappers, running Java Hadoop jobs, combiners.<html></td>
 +</tr>
 +</table>
 +</html>
  

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