[{"logfile1(unknown)":[1,2,3]},{"logFile2(unknown)":[4,5,6]}]

db.collection.aggregate([{$group:{_id:"$_id",new:{$first:"$$ROOT"}}},{"$project":{"map":{"$objectToArray":"$new"}}},{$unwind:"$map"},{$match:{"map.k":{"$ne":"_id"}}}])