导读本文略长,主要解决以下几个疑问1、聚集索引里都存储了什么宝贝2、什么时候索引层高会发生变化3、预留的1/16空闲空间做什么用的4、记录被删除后的空间能回收重复利用吗1、背景信息1.1 关于innodb_fill_factor有个选项 innodb_fill_factor 用于定义InnoDB page的填充率,默认值是100,但其实最高只能填充约15KB的数据,因为InnoDB会预留1/16的空闲空间。在InnoDB文档中,有这么一段话An innodb_fill_factor setting of 100 leaves 1/16 of the space in clustered index pages free for future index growth.另外,文档中还有这样一段话When new records are inserted into an InnoDB clustered index, InnoDB tries to leave 1/16 of the page free for future insertions and updates of the index records. If index records are inserted in a sequential order (ascending or descending
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