A table reference count was introduced in MySQL 5.6 to serve two purposes:

• Allow tables to be evicted from the InnoDB data dictionary cache: dict_sys.evict_table_LRU()
• After FLUSH TABLES, allow InnoDB persistent statistics to be reloaded. This logic would be simplified in MDEV-35000.

If as part of MDEV-25292 we will change the metadata lock acquisition in DDL operations, we could fully protect the purge of committed InnoDB history with metadata locks and would not need any reference counts.

Then, the dict_sys.evict_table_LRU() could then be made event-based, coupled more tightly with the table definition cache and FLUSH TABLES. This would reduce periodic contention on dict_sys.latch.