updateToMongoField :: (PersistEntity record, PersistEntityBackend record ~ DB.MongoContext)
                   => Update record -> DB.Field
updateToMongoField (Update field v up) = updateToBson (fieldName field) (toPersistValue v) (Left up)
updateToMongoField :: (PersistEntity record, PersistEntityBackend record ~ DB.MongoContext)
                   => Update record -> DB.Field
updateToMongoField (Update field v up) = updateToBson (fieldName field) (toPersistValue v) (Left up)
updateToMongoField (Update field v up) = updateToBson (fieldName field) (toPersistValue v) (Left up)