http://aadant.com/blog/2014/02/04/how-to-calculate-a-specific-innodb-index-size/
在 mysql中 ,使用
show table status like '表名'\G;可以看出具体表的情况,比如:
Name: t
Engine: InnoDB
Version: 10
Row_format: Compact
Rows: 4186170
Avg_row_length: 34
Data_length: 143310848
Max_data_length: 0
Index_length: 146030592
Data_free: 6291456
Auto_increment: NULL
Create_time: 2014-02-04 15:40:54
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)
其中可以看出Data_length和Index_length,显示的是索引段的总的大小,那么一个表中如果有多个索引,要如何查看某个索引的大小,页呢?可以使用SQL语句完成,但要先分析下表,步骤如下:
CREATE TABLE `t` ( `a` smallint(6) DEFAULT NULL, `b` smallint(6) DEFAULT NULL, `c` smallint(6) DEFAULT NULL, KEY `a` (`a`), KEY `b` (`b`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1
ANALYZE table t; SELECT sum(stat_value) pages, index_name, sum(stat_value) * @@innodb_page_size size FROM mysql.innodb_index_stats WHERE table_name = 't' AND database_name = 'test' AND stat_description = 'Number of pages in the index' GROUP BY index_name; +-------+-----------------+-----------+ | pages | index_name | size | +-------+-----------------+-----------+ | 8747 | GEN_CLUST_INDEX | 143310848 | | 4456 | a | 73007104 | | 4457 | b | 73023488 | +-------+-----------------+-----------+ 3 rows in set (0.00 sec)
其中用到的是mysql 5.6中的 mysql.innodb_table_stats和mysql.innodb_index_stats表 ,里面有很多有用的统计信息
要注意的是,上面的方法对于分区表也是同样适用的