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From Apache Wiki <wikidi...@apache.org>
Subject [Lucene-hadoop Wiki] Update of "RandomWriter" by HairongKuang
Date Wed, 28 Jun 2006 20:59:23 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Lucene-hadoop Wiki" for change notification.

The following page has been changed by HairongKuang:

New page:
'''RandomWriter''' example

''RandomWriter" example implements a distributed random writer. Each map takes a file name
as input and writes one Gig of random data to the DFS sequence file by generating multiple
records, each with a random key and a random value. A mapper does not emit any output and
the reduce phase is null.

This example uses a useful pattern for dealing with Hadoop's constraints on !InputSplits.
Since each input split can only consist of a file and byte range and we want to control how
many maps there are (and we don't really have any inputs), we create a directory with a set
of artificial files, each of which contains the filename that we want a given map to write
to. Then, using the text line reader and this "fake" input directory, we generate exactly
the right number of maps. Each map gets a single record that is the filename, to which it
is supposed to write its output. 

To run the example, the command syntax is[[BR]]
bin/hadoop org.apache.hadoop.examples.RandomWriter <out-dir> [<configuration file>]

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