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Posted to commits@cassandra.apache.org by Apache Wiki <wi...@apache.org> on 2010/10/25 18:55:57 UTC

[Cassandra Wiki] Trivial Update of "HadoopSupport" by jeremyhanna

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The "HadoopSupport" page has been changed by jeremyhanna.
http://wiki.apache.org/cassandra/HadoopSupport?action=diff&rev1=17&rev2=18

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  == MapReduce ==
  
  ==== Input from Cassandra ====
- Cassandra 0.6 (and later) adds support for retrieving data from Cassandra.  This is based on implementations of [[http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/InputSplit.html|InputSplit]], [[http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/InputFormat.html|InputFormat]], and [[http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/RecordReader.html|RecordReader]] so that Hadoop MapReduce jobs can retrieve data from Cassandra.  For an example of how this works, see the contrib/word_count example in 0.6 or later.  Cassandra rows or row  fragments (that is, pairs of key + `SortedMap`  of columns) are input to Map tasks for  processing by your job, as specified by a `SlicePredicate`  that describes which columns to fetch from each row.
+ Cassandra 0.6 (and later) adds support for retrieving data from Cassandra.  This is based on implementations of [[http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/InputSplit.html|InputSplit]], [[http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/InputFormat.html|InputFormat]], and [[http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/RecordReader.html|RecordReader]] so that Hadoop !MapReduce jobs can retrieve data from Cassandra.  For an example of how this works, see the contrib/word_count example in 0.6 or later.  Cassandra rows or row  fragments (that is, pairs of key + `SortedMap`  of columns) are input to Map tasks for  processing by your job, as specified by a `SlicePredicate`  that describes which columns to fetch from each row.
  
  Here's how this looks in the word_count example, which selects just one  configurable columnName from each row: