mapReduce SO 38255279

 db.matches.mapReduce(
   function map() {
     var doc = this;
     doc.sets = doc.sets.filter(function (set) {
       return doc.tournament === 'Wimbledon' ? !set.tiebreak : set.tiebreak;
     });
     emit(doc._id, doc);
   },
   function reduce(){},
   {
     query: {
       $and: [{
         "sets.tiebreak": true,
       }, {
         "sets.tiebreak": false
       }],
       $or: [{
         "tournament": "Wimbledon"
       }, {
         "tournament": "Roland Garros"
       }]
     },
     out: "result"
   });
 db.result.find();