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版主们，求show processlist疑问

剑心永远OK 2011-10-15 02:35:14

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？

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切换为时间正序

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剑心永远OK 2011-10-17

这是一条经常出现在show processlist里面的SQL



SELECT 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。

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剑心永远OK 2011-10-16

[Quote=引用 2 楼 zuoxingyu 的回复:]

引用楼主 dada20042030 的回复:

这几条SQL一直导致CPU占用100%以上。。找不到解决思路，

单独分析这几条语句。
[/Quote]
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。

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