MySQL 8 Administrator???s Guide

Manual changes required before downgrading

This section describes some of the changes that need to be executed manually by the user before downgrading:

• System table changes: MySQL 5.7 manages individual tablespace for system tables while in MySQL 8, system tables were migrated into a single tablespace file known as mysql.ibd. So, before downgrading to MySQL 5.7, move the system table back to the individual tablespace files with the following commands:

        ALTER TABLE mysql.columns_priv TABLESPACE=innodb_file_per_table;         ALTER TABLE mysql.component TABLESPACE=innodb_file_per_table;         ALTER TABLE mysql.db TABLESPACE=innodb_file_per_table;         ALTER TABLE mysql.default_roles TABLESPACE=innodb_file_per_table;         ALTER TABLE mysql.engine_cost TABLESPACE ...