[{"_id":ObjectId("5a934e000102030405000000"),"subDoc":[{"a":1,"subArray":[1,2,3]},{"b":2}]},{"_id":ObjectId("5a934e000102030405000001"),"subDoc":[{"a":1,"subArray":[4,5,6]},{"b":2},{"c":3,"subArray":[8,8,8]}]}]

db.collection.find()