def sync(alias, only_model=None):
    engine = get_engine_from_db_alias(alias)

    if engine != 'django_cassandra_engine':
        raise CommandError('Database {} is not cassandra!'.format(alias))

    connection = connections[alias]
    connection.connect()
    keyspace = connection.settings_dict['NAME']

    _logger.info('Creating indexes in {} [CONNECTION {}] ..'.format(
        keyspace, alias))

    connection.connection.cluster.refresh_schema_metadata()
    connection.connection.cluster.schema_metadata_enabled = True

    indexes_by_model = UnifiedIndex().get_indexes()

    for app_name, app_models \
            in connection.introspection.cql_models.items():
        for model in app_models:
            # If the app model is registered as a SearchIndex
            if model in indexes_by_model:
                model_name = "{0}.{1}".format(model.__module__, model.__name__)
                if not only_model or model_name == only_model:
                    _logger.info("Creating index %s.%s".format(
                        app_name, model.__name__))
                    _logger.info(
                        "Index class associated to te model {0}.{1}".format(
                            app_name,
                            indexes_by_model.get(model).__class__.__name__))
                    create_index(model, indexes_by_model.get(model))