查找用不到的索引

mysql> select version()\G
*************************** 1. row ***************************
version(): 5.7.25-TiDB-v6.2.0-alpha
1 row in set (0.00 sec)

mysql> select * from mysql.SCHEMA_INDEX_USAGE;
Empty set (0.00 sec)

mysql> select * from INFORMATION_SCHEMA.SCHEMA_INDEX_USAGE;
ERROR 1146 (42S02): Table 'information_schema.SCHEMA_INDEX_USAGE' doesn't exist