[{"_id":1,"location":"abc","type":"456"},{"_id":2,"type":"123","language":"english"},{"_id":3,"location":"ghi","type":"9876","language":"latin"},{"_id":4,"language":"hebrew","type":"9434"},{"_id":5,"type":"525","location":"cari"},{"_id":6,"language":"spanish","location":"dff"},{"_id":7,"location":"adpj","type":"3463","language":"english"},{"_id":8,"language":"french","location":"nts"}]

db.collection.aggregate([{$match:{"type":{"$exists":true},"location":{"$exists":true},"language":{"$exists":true}}},{$group:{"_id":{"location":"$location","type":"$typ","language":"$language"},"count":{$sum:1}}}])