[{"_id":{"userArea":NumberInt(4927)},"pages":{"12":{"page":NumberInt(2635),"progress":"COMPLETED","progressType":"USER_PROGRESS","end":11},"13":{"page":NumberInt(2627),"progress":"COMPLETED","progressType":"USER_PROGRESS",/**"end": ISODate("2018-04-19T15:04:29.000+0000")*/}}}]

db.collection.aggregate([{"$project":{"p":{"$objectToArray":"$pages"}}},{"$unwind":"$p"},{"$match":{"p.v.progress":"COMPLETED"}},{"$group":{"_id":"$_id","p":{"$addToSet":"$p"}}},{$project:{"a":{"$arrayToObject":"$p"}}},{"$replaceRoot":{"newRoot":"$a"}}])