public function delete_thread($nosql, $hkey_thread) {
    $sql  = "UPDATE zindex_thread1";
    $sql .= "   SET flag = 'D', time_tolive = NOW()";
    $sql .= " WHERE hkey_thread = '" . $hkey_thread . "';";
    if (mysql_query($sql) === FALSE) return FALSE;
    $sql  = "UPDATE zindex_message1";
    $sql .= "   SET flag = 'D', time_tolive = NOW()";
    $sql .= " WHERE hkey_thread = '" . $hkey_thread . "';";
    return (mysql_query($sql) !== FALSE);
}