/**
  * @return self
  */
 public static function newPurgeTask()
 {
     global $wgCityId;
     $task = new self();
     $task->call('purgeExpiredRows');
     $task->wikiId($wgCityId);
     $task->title(\SpecialPage::getTitleFor('Recentchanges'));
     $task->queue();
     return $task;
 }