MySQLSQL优化：碍手碍脚的索引_MySQL-Mysql Tutorial-php.cn

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MySQLSQL优化：碍手碍脚的索引_MySQL

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Jun 01, 2016 pm 01:17 PM

database

该篇是SQL优化的第4篇。

这里主要表达我的一个观点是：不该存在的索引就该干掉，留着碍事

在2014-3-12 15:39:01 -- 15:55:00这段时间内，在某个业务系统我们发现2个问题：

这种现象在数据库中实际也是很常见，就是某个慢查询，始作俑者，执行特马慢，把后面本该很快的查询给堵住，导致系列长查询出现

经诊断，我们发现某张表里存在dateline索引，该索引会让MySQL优化器选择错了执行计划，导致后续大量SQL拥堵，大概有5000条Query相互堵住

如果不走dateline索引，效果很好，下面对比：

1. 执行计划对比

2. 执行时间对比：

因此，我们给开发童鞋的反馈是，卡擦掉dateline索引

起初我们并不知道该索引是否还提供给其他Query使用，所以胆战心惊害怕会引起其他查询变慢

不过经过这段时间的观察，实际上，并没有其他查询在使用这条索引

索引是好东西，但不要贪哦

Good Luck！

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