/**
  * @param User $user
  */
 protected function saveUserCustomFields(User $user)
 {
     $this->conn->executeUpdate('DELETE FROM ' . $this->conn->quoteIdentifier($this->userCustomFieldsTableName) . ' 
         WHERE ' . $this->getUserColumns('user_id') . ' = ?', array($user->getId()));
     foreach ($user->getCustomFields() as $attribute => $value) {
         $this->conn->executeUpdate('INSERT INTO ' . $this->conn->quoteIdentifier($this->userCustomFieldsTableName) . ' (' . $this->getUserColumns('user_id') . ', ' . $this->getUserColumns('attribute') . ', ' . $this->getUserColumns('value') . ') VALUES (?, ?, ?) ', array($user->getId(), $attribute, $value));
     }
 }