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原帖由 meizhe1981 于 2008-12-2 09:33 发表 ![]()
这个方法依然无法避免filesort,不信你可以试试
那是你没有强制索引!
root:test> explain select * from test force index(i_inverse) where userid in (1,2) order by inverse asc;
+----+-------------+-------+-------+---------------+-----------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+---------------+-----------+---------+------+------+-------------+
| 1 | SIMPLE | test | index | NULL | i_inverse | 8 | NULL | 7 | Using where |
+----+-------------+-------+-------+---------------+-----------+---------+------+------+-------------+
就这个SQL原型而言,需要分开建,不可能又兼顾filesort的压力,又兼顾查询结果集的压力,只能看需求取其一!
否则就是改业务,改SQL
[ 本帖最后由 talen-t 于 2008-12-2 13:05 编辑 ] |
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