public function getUnreadPmList($forumUserId)
 {
     $key = Util_MemCacheKey::get_myanjuke_noreadmess_list($forumUserId);
     APF::get_instance()->benchmark_begin(__CLASS__ . " get mess ");
     $memcache = APF_Cache_Factory::get_instance()->get_memcache();
     $list = $memcache->get($key);
     if (!$list) {
         $time = Util_MemCacheTime::get_myanjuke_noreadmess_list();
         $list = parent::getUnreadPmList($forumUserId);
         $memcache->add($key, $list, 0, $time);
     }
     APF::get_instance()->benchmark_end(__CLASS__ . " get mess ");
     return $list;
 }