版主们，求show processlist疑问

Question

利用mytop监测mysql运行状态，发现有几句经常会出现在里面，时间不长，1秒的时候就会消失了。我随后拿着这几条SQL来单测试，速度都在0点几秒时间内。之后我发现show processlist，状态是处于preparing状态，然后消失。。网上搜索了很多都很少关于preparing状态的介绍，只是在MYSQL手册里面简单描述了，在运行中进行优化。这几条SQL一直导致CPU占用100%以上。。找不到解决思路，问preparing是怎么回事，各大虾有什么思路不？

Answer 1

先找找这几个paeparing得是否正常语句

Answer 2

分析了，速度都在0点几秒以内。
不过有样东西就是explain出来的东西，我觉得有点奇怪
explain select count(*) total from product p left join product_description pd on (p.product_id = pd.product_id) where pd.language_id = 1 and p.product_id IN (SELECT p2c.product_id FROM product_to_category p2c WHERE p2c.category_id = '218' or p2c.category_id = '220');+----+--------------------+-------+----------------+--------------------------------+------------+---------+--------------------------------+------+--------------------------+
| id | select_type        | table | type           | possible_keys                  | key        | key_len | ref                            | rows | Extra                    |
+----+--------------------+-------+----------------+--------------------------------+------------+---------+--------------------------------+------+--------------------------+
|  1 | PRIMARY            | p     | index          | PRIMARY                        | PRIMARY    | 4       | NULL                           | 9771 | Using where; Using index |
|  1 | PRIMARY            | pd    | eq_ref         | PRIMARY                        | PRIMARY    | 8       | fashione_db.p.product_id,const |    1 | Using where; Using index |
|  2 | DEPENDENT SUBQUERY | p2c   | index_subquery | PRIMARY,category_id,product_id | product_id | 4       | func                           |    1 | Using where              |
+----+--------------------+-------+----------------+--------------------------------+------------+---------+--------------------------------+------+--------------------------+explain 出来的结果里面有个表product的type类型是index,这叫正常吗？而且检索的行也很多。。我感觉不正常。

Answer 3

这是一条经常出现在show processlist里面的SQLSELECT COUNT(*) AS total FROM product p LEFT JOIN product_description pd ON (p.product_id = pd.product_id) LEFT JOIN product_to_store p2s ON (p.product_id = p2s.product_id) LEFT JOIN product_special ps ON (p.product_id = ps.product_id)  WHERE pd.language_id = '1' AND p.status = '1' AND p.date_available <= NOW() AND p2s.store_id = '0' AND p.product_id IN (SELECT p2c.product_id FROM product_to_category p2c WHERE p2c.category_id = '107' OR p2c.category_id = '77' OR p2c.category_id = '75' OR p2c.category_id = '74' OR p2c.category_id = '71' OR p2c.category_id = '70' OR p2c.category_id = '69' OR p2c.category_id = '7');
explain+----+--------------------+-------+----------------+--------------------------------+------------+---------+----------------------------------+------+--------------------------+
| id | select_type        | table | type           | possible_keys                  | key        | key_len | ref                              | rows | Extra                    |
+----+--------------------+-------+----------------+--------------------------------+------------+---------+----------------------------------+------+--------------------------+
|  1 | PRIMARY            | p2s   | index          | PRIMARY,store_id               | PRIMARY    | 8       | NULL                             | 7360 | Using where; Using index |
|  1 | PRIMARY            | p     | eq_ref         | PRIMARY,date_available         | PRIMARY    | 4       | fashione_db.p2s.product_id       |    1 | Using where              |
|  1 | PRIMARY            | ps    | ref            | product_id                     | product_id | 4       | fashione_db.p.product_id         |    1 | Using index              |
|  1 | PRIMARY            | pd    | eq_ref         | PRIMARY                        | PRIMARY    | 8       | fashione_db.p2s.product_id,const |    1 | Using where; Using index |
|  2 | DEPENDENT SUBQUERY | p2c   | index_subquery | PRIMARY,category_id,product_id | product_id | 4       | func                             |    1 | Using where              |
+----+--------------------+-------+----------------+--------------------------------+------------+---------+----------------------------------+------+--------------------------+
5 rows in set (0.00 sec)
检索有7000多条。。感觉不太好，但应该不会导致CPU那么高啊。求解释。