[{"collection":"first","count":3,"content":{"_id":{"type":"autoincrement","autoType":"int","start":1},"field1":{"type":"int","min":1,"max":2},"field2":{"type":"string","minLength":1,"maxLength":1}}},{"collection":"second","count":2,"content":{"_id":{"type":"autoincrement","autoType":"int","start":0},"count":{"type":"valueAggregator","database":"test","collection":"first","key":"field2","values":{"field1":"$$_id"}}}}]

db.first.find()