The reduce output field list spec is under attribute 
 * "mapreduce.fieldsel.reduce.output.key.value.fields.spec".
 * 
 * The reducer extracts output key/value pairs in a similar manner, except that
 * the key is never ignored.
The reduce output field list spec is under attribute 
 * "mapreduce.fieldsel.reduce.output.key.value.fields.spec".
 * 
 * The reducer extracts output key/value pairs in a similar manner, except that
 * the key is never ignored. | FieldSelectionMapReduce.java