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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> select version(); +------------+ | version() | +------------+ | 5.6.36-log | +------------+ 1 row in set (0.02 sec) mysql> select database(); +------------+ | database() | +------------+ | mytest | +------------+ 1 row in set (0.00 sec) mysql> show tables; +------------------+ | Tables_in_mytest | +------------------+ | customer | | district | | history | | item | | new_orders | | order_line | | orders | | stock | | warehouse | +------------------+ 9 rows in set (0.00 sec) mysql> show variables like 'innodb_page_size'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | innodb_page_size | 8192 | +------------------+-------+ 1 row in set (0.04 sec)
3. 查询
* 查询每张表primary key对应的root page_no
mysql> select t.table_id table_id, t.name table_name, i.page_no root_page_no from information_schema.INNODB_SYS_INDEXES i, information_schema.INNODB_SYS_TABLES t where i.table_id = t.table_id and i.name = 'PRIMARY' and t.name like '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 | +----------+-------------------+--------------+ 8 rows in set (0.04 sec)
* 查询order_line表数据量
mysql> select count(1) from order_line; +----------+ | count(1) | +----------+ | 6001615 | +----------+ 1 row in set (9.03 sec)
* 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@localhost src]# hexdump -s 24640 -n 2 -C /data/mysql_data_6/mytest/order_line.ibd; 00006040 00 02 |..| 00006042
4. B+Tree
高度 | 非叶节点数 | 叶节点数 | 数据行数 | 占用空间 |
1 | 0 | 1 | 468 | 16.0KiB |
2 | 1 | 1203 | > 563 thousand | 18.8MiB |
3 | 1204 | 1447209 | > 677 million | 22.1GiB |
4 | 1448413 | 1740992427 | > 814 billion | 25.9TiB |
5. xxx
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