function add($compile = true)
 {
     if (!isset($this->url)) {
         return $this->_error('url');
     }
     $this->host = null;
     if (!($query = $this->_buildQuery())) {
         return false;
     }
     if (!$query->hasAttribute('referred')) {
         $query->setAttribute('referred', 'UNIX_TIMESTAMP()');
     }
     if (!$query->insert()) {
         return $this->_error('insert');
     }
     if ($compile) {
         RefererStatistics::compile($this->host);
     }
     return true;
 }