text: function createDiffWords(query) {
  
  	db.getCollection(query['collection_source']).find({}).forEach( function( data ) {
  	  var word = db.getCollection(query['collection_comp']).findOne({'word': data.word});
  
  	  if(!word) {
  	    db.getCollection(query['collection_diff']).insert(data);
  	  }  
  	})
  
  }