You can retrieve the index size for tables, partitions, or subpartitions can using the innodb_index_stats table. In the following example, index sizes are retrieved for table t1. For a definition of table t1 and corresponding index statistics, see Section 15.8.10.1.6, “InnoDB Persistent Statistics Tables Example”.

mysql> SELECT SUM(stat_value) pages, index_name,
SUM(stat_value)*@@innodb_page_size size
FROM mysql.innodb_index_stats WHERE table_name='t1'
AND stat_name = 'size' GROUP BY index_name;
+-------+------------+-------+
| pages | index_name | size  |
+-------+------------+-------+
|     1 | PRIMARY    | 16384 |
|     1 | i1         | 16384 |
|     1 | i2uniq     | 16384 |
+-------+------------+-------+

For partitions or subpartitions, you can use the same query with a modified WHERE clause to retrieve index sizes. For example, the following query retrieves index sizes for partitions of table t1:

mysql> SELECT SUM(stat_value) pages, index_name,
SUM(stat_value)*@@innodb_page_size size
FROM mysql.innodb_index_stats WHERE table_name like 't1#P%'
AND stat_name = 'size' GROUP BY index_name;