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courses:mapreduce-tutorial:step-23 [2012/01/27 20:37]
straka |
courses:mapreduce-tutorial:step-23 [2012/01/31 14:33] (current)
dusek |
| * ''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 ===== |
| |
| ===== Output formats ===== | ===== Output formats ===== |
| An input format is a subclass of [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapreduce/lib/output/FileOutputFormat.html|FileOutputFormat<K,V>]], where //K// is the type of keys and //V// is the type of values it can store. | An output format is a subclass of [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapreduce/lib/output/FileOutputFormat.html|FileOutputFormat<K,V>]], where //K// is the type of keys and //V// is the type of values it can store. |
| |
| Available output formats: | Available output formats: |
| * ''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> |
| |
