1. 背景

* 在InnoDB存储引擎中，表都是根据主键顺序组织存放的，这种存储方式的表称为索引组织表(index organized table IOT)。

* 在InnoDB存储引擎中，每张表都有个主键(Primary key)，如果在创建表时没有地定义主键，则InnoDB存储引擎会选择表中符合条件的列或隐式创建主键。

2. 环境

mysql>selectversion();+------------+|version()|+------------+|5.6.36-log|+------------+1rowinset(0.02sec)mysql>selectdatabase();+------------+|database()|+------------+|mytest|+------------+1rowinset(0.00sec)mysql>showtables;+------------------+|Tables_in_mytest|+------------------+|customer||district||history||item||new_orders||order_line||orders||stock||warehouse|+------------------+9rowsinset(0.00sec)mysql>showvariableslike'innodb_page_size';+------------------+-------+|Variable_name|Value|+------------------+-------+|innodb_page_size|8192|+------------------+-------+1rowinset(0.04sec)

3. 查询

* 查询每张表primary key对应的root page_no

mysql>selectt.table_idtable_id,t.nametable_name,i.page_noroot_page_nofrominformation_schema.INNODB_SYS_INDEXESi,information_schema.INNODB_SYS_TABLEStwherei.table_id=t.table_idandi.name='PRIMARY'andt.namelike'mytest/%';+----------+-------------------+--------------+|table_id|table_name|root_page_no|+----------+-------------------+--------------+|22|mytest/customer|3||21|mytest/district|3||27|mytest/item|3||24|mytest/new_orders|3||26|mytest/order_line|3||25|mytest/orders|3||28|mytest/stock|3||20|mytest/warehouse|3|+----------+-------------------+--------------+8rowsinset(0.04sec)

* 查询order_line表数据量

mysql>selectcount(1)fromorder_line;+----------+|count(1)|+----------+|6001615|+----------+1rowinset(9.03sec)

* 通过表数据文件order_line.ibd获取高度 [跳过 root_page_no * innodb_page_size + 64, 获取2字节长度就是树的高度]

由此可得树的高度为3, 高度标记从0开始

[root@localhostsrc]#hexdump-s24640-n2-C/data/mysql_data_6/mytest/order_line.ibd;000060400002|..|00006042

4. B+Tree

5. xxx