mysql查询优化/检索每个组中的最后一条记录

Question

有没有办法优化这个mysql查询？ 我在表格中有大约100K行。

select  komentarai.* FROM (
  SELECT MAX(id) AS max_id FROM komentarai WHERE siteid=1 GROUP BY number 
) AS tbl
INNER JOIN `komentarai` ON komentarai.id = tbl.max_id ORDER BY komentarai.added DESC LIMIT XX, 10

以下是对索引的解释：

PRIMARY <derived2> ALL NULL NULL NULL NULL 3372 Using temporary; Using filesort
PRIMARY komentarai eq_ref PRIMARY,id PRIMARY 4 tbl.max_id 1 2
DERIVED komentarai ref siteid siteid 1 5695 Using where; Using temporary; Using filesort

谢谢！