Map/Reduce no Mongo para coleção de Posts

gistfile1.js

map = function() { 
  this.textContent.split(' ').forEach( 
    function(word){ emit(word,1); } 
  );
};

reduce = function(key, values) { 
  var count = 0; 
  values.forEach(
    function(value) { count += value; }
  ); 
  return count; 
};

db.posts.mapReduce(map, reduce, {out : {replace:"results"}});

db.result.find().limit(10).sort({value:-1})