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The following page has been changed by JackHebert:
http://wiki.apache.org/lucene-hadoop/HadoopMapReduceSequenceFileFormat

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== Sequence File Format ==

A complex project using Hadoop often requires multiple map-reduces to happen in 
series. While the input data may be textual, it is extremely helpful to 
maintain intermediate data in the SequenceFile format.

SequenceFile's allow you to skip avoid parsing lines of input data into <key, 
value> pairs. Instead, the mapper will receive the exact <key, value> pairs 
that were emitted by the reducer who created the data. 

This format is easily used by setting the output format of a job to be 
SequenceFileOutputFormat: 
JobConf.setOutputFormat(SequenceFileOutputFormat.class), and setting all 
successive jobs to use SequenceFileInputFormat: 
JobConf.setInputFormat(SequenceFileInputFormat.class). 

While the files are not exactly human readable, their use greatly eases the 
implementation of map reduce sequences.

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