[{"collection":"test","count":5,"content":{"str":{"type":"string","minLength":1,"maxLength":1},"date":{"type":"date"},"number":{"type":"int"}},"indexes":[{"name":"missing_index","key":{"cheese":1}}]}]

db.test.aggregate([{$match:{$or:[{cheese:{"$exists":true}},{cheese:{"$exists":false}}]}}]).explain()