Samples of CouchDB and Riak MapReduce

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Some notes from a workshop on CouchDB and Riak diving into their support for MapReduce. While the code might not look the same, if you pay close attention you’ll notice it is almost identical. Except Riak, MapReduce functions need to “deserialize” data.

Riak code

CouchDB code

  view :delta_yeas_nays,
       :map            => “function(doc){ emit(doc._id, (doc.yeas || 0) - (doc.nays || 0)); }”,
       :reduce         => “function(keys, values){ return sum(values) }”,
       :type           => :raw,
       :include_docs   => false,
       :results_filter => lambda {|results| results[‘rows’].first[‘value’] }

In case you cannot see the code, please try refreshing the page. It looks like sometimes the syntax highlighter doesn’t load correctly :-(.

via: http://vermonster.com/2010/03/31/nosql-workshop-featuring-riak-and-couchdb/

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by Alex Popescu

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