MySQL 9.4 Release Notes
These views display indexes for which there are no events, which indicates that they are not being used. By default, rows are sorted by schema and table.
This view is most useful when the server has been up and processing long enough that its workload is representative. Otherwise, presence of an index in this view may not be meaningful.
The schema_unused_indexes view
has these columns:
object_schemaThe schema name.
object_nameThe table name.
index_nameThe unused index name.