Select多行SQL语句慢查询优化
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2024-02-03 19:34:16
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环境：MySQL5.5 InnoDB表
post ，主键为 id
需求非常简单，根据id返回 post.name ，需要一次返回指定的多个，所以使用了where id in：
select `name` from `post` where `id` in(2142324,2106574,2106564,2075699,2065402,2050790,2038346,2038345,2035588,2031765,2022035,2022034,2020745,2020737,2020718,1987558,1970241,1962232,1911342,1891481,1889641,1877438,1877434,1867217,1866057,1866013,1847315);
Explain结果：
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| 1 | SIMPLE | post | range | PRIMARY | PRIMARY | 4 | NULL | 27 | Using where |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
现在这句SQL一小时产生几千条慢查询记录，我直接在console执行每次也需要7,8秒
能怎么优化呢？
回复内容：
环境：MySQL5.5 InnoDB表 post ，主键为 id
需求非常简单，根据id返回 post.name ，需要一次返回指定的多个，所以使用了where id in：
select `name` from `post` where `id` in(2142324,2106574,2106564,2075699,2065402,2050790,2038346,2038345,2035588,2031765,2022035,2022034,2020745,2020737,2020718,1987558,1970241,1962232,1911342,1891481,1889641,1877438,1877434,1867217,1866057,1866013,1847315);
Explain结果：
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| 1 | SIMPLE | post | range | PRIMARY | PRIMARY | 4 | NULL | 27 | Using where |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
现在这句SQL一小时产生几千条慢查询记录，我直接在console执行每次也需要7,8秒
能怎么优化呢？
从纯sql的角度看是没问题的，走了索引，rows值也不大，如果速度很慢，可以从3个方面看 1：innodb参数是否已经优化，比如innodbbufferpoor_size等 2：qcache命中率。根据你上诉问题，一小时该语句产生几千条慢查询，命中率明显不高，是否该表写入频率过高导致qcache失效，是否考虑读写分离 3：数据量大的话考虑分区，或者水平分表