desc和asc同时排序很慢

Question

当我使用'ORDER BY datetime DESC和sticky ASC'同时查询速度很慢在forum_threads中有~200.000行。

列

+----+-------------+---------+---------+---------+--------+--------+---------+----------+
| id | category_id | user_id | subject | message | sticky | closed | deleted | datetime |
+----+-------------+---------+---------+---------+--------+--------+---------+----------+

此查询的速度为0.2秒（ORDER BY datetime DESC，sticky ASC）

SELECT * FROM forum_threads WHERE deleted = 0 ORDER BY datetime DESC, sticky ASC LIMIT 0, 30

此查询的速度为0.0008sec（ORDER BY datetime DESC）

SELECT * FROM forum_threads WHERE deleted = 0 ORDER BY datetime DESC, sticky ASC LIMIT 0, 30

索引：

如何更快地完成第一个查询？

Joery。