db={"orders":[{"_id":NumberLong(2761632),"data":{"field.with.dots":{}}},{"_id":NumberLong(2761633),"test":{"a":"a","b":"b","c":"c","v0.0.1":"ok"}}],"meta":[{"by":"steevej","at":"gmail","dot":"com","for":"how-to-use-unset-when-the-key-being-removed-contains-a-dot-in-its-name"}]}

db.orders.update({"test":{$exists:true}},[{"$unset":["test.a","test.b"]},{$set:{"_tmp.toArray":{"$objectToArray":"$test"}}},{$set:{"_tmp.filtered":{"$filter":{"input":"$_tmp.toArray","cond":{"$ne":["$$this.k","v0.0.1"]}}}}},{$set:{"_tmp.toObject":{"$arrayToObject":"$_tmp.filtered"}}},{"$set":{"test":"$_tmp.toObject"}}])