织梦如何按照软件下载次数排列

织梦的arclist标签可以按照文章点击次数、发布日期、得分等进行排序，今天有个客户需要按照软件下载次数进行排列，于是做了简单二次开发，首先找到include目录下面的taglib目录里的arclist.lib.php文件在376行后加入如下代码
 if($orderby == 'down')
 {
  $sql = "select SUM(downloads) as down_num,id from dede_downloads group by id ORDER BY down_num DESC LIMIT 0,15";
  $dsql->Execute('me',$sql);
  while($drow = $dsql->GetArray() )
  {
   $arr[] = $drow['id'];
  }
  $dstr = implode(",",$arr);
  if($orwhere!='')
  {
   $orwhere .= " AND arc.id in($dstr)";
  }else{
   $orwhere .= " where arc.id in($dstr)";
  }
  $ordersql = 'ORDER BY field(arc.id,'.$dstr.')';
 }