[{"_id":"AQ","arr_delay":262421.0,"carrier_delay":144922.0,"weather_delay":2297.0,"nas_delay":15933.0,"security_delay":1871.0,"late_aircraft_delay":97398.0}]

db.collection.aggregate([{"$addFields":{minField:{$reduce:{input:{"$filter":{"input":{"$objectToArray":"$$ROOT"},as:"field",cond:{"$setIsSubset":[[{$type:"$$field.v"}],["double","decimel",]]}}},initialValue:{name:null,minVal:null},in:{name:{$cond:[{$lt:["$$this.v","$$value.minVal"]},"$$this.k","$$value.name"]},minVal:{$min:["$$this.v","$$value.minVal"]}}}}}},{"$addFields":{"minField":"$minField.name"}}])