def determine_keep_history(cursor, keep_history=None):
    """Determine whether the RelStorage databases is set to keep history.
    """
    if keep_history is None:
        # We don't know, so sniff
        cursor.execute(
            "select 1 from pg_catalog.pg_class "
            "where relname = 'current_object'")
        keep_history = bool(list(cursor))

    return keep_history