启用 stage/innodb/alter% 工具：Enable the stage/innodb/alter% instruments:

mysql> UPDATE performance_schema.setup_instruments
       SET ENABLED = 'YES'
       WHERE NAME LIKE 'stage/innodb/alter%';
Query OK, 7 rows affected (0.00 sec)
Rows matched: 7  Changed: 7  Warnings: 0

启用阶段事件消费者表，其中包括 events_stages_current、events_stages_history 和 events_stages_history_long。Enable the stage event consumer tables, which include events_stages_current, events_stages_history, and events_stages_history_long.

mysql> UPDATE performance_schema.setup_consumers
       SET ENABLED = 'YES'
       WHERE NAME LIKE '%stages%';
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3  Changed: 3  Warnings: 0

执行 ALTER TABLE 操作。在本例中，在 employees 示例数据库的 employees 表中添加一个 middle_name 列。Run an ALTER TABLE operation. In this example, a middle_name column is added to the employees table of the employees sample database.

mysql> ALTER TABLE employees.employees ADD COLUMN middle_name varchar(14) AFTER first_name;
Query OK, 0 rows affected (9.27 sec)
Records: 0  Duplicates: 0  Warnings: 0

通过查询性能模式 events_stages_current 表来检查 ALTER TABLE 操作的进度。显示的阶段事件根据当前正在进行的 ALTER TABLE 阶段而有所不同。WORK_COMPLETED 列显示已完成的工作量。WORK_ESTIMATED 列提供剩余工作量的估计。Check the progress of the ALTER TABLE operation by querying the Performance Schema events_stages_current table. The stage event shown differs depending on which ALTER TABLE phase is currently in progress. The WORK_COMPLETED column shows the work completed. The WORK_ESTIMATED column provides an estimate of the remaining work.

mysql> SELECT EVENT_NAME, WORK_COMPLETED, WORK_ESTIMATED
       FROM performance_schema.events_stages_current;
+------------------------------------------------------+----------------+----------------+
| EVENT_NAME                                           | WORK_COMPLETED | WORK_ESTIMATED |
+------------------------------------------------------+----------------+----------------+
| stage/innodb/alter table (read PK and internal sort) |            280 |           1245 |
+------------------------------------------------------+----------------+----------------+
1 row in set (0.01 sec)

events_stages_current 表在 ALTER TABLE 操作完成后返回空集。在这种情况下，您可以检查events_stages_history 表，以查看已完成操作的事件数据。例如：The events_stages_current table returns an empty set if the ALTER TABLE operation has completed. In this case, you can check the events_stages_history table to view event data for the completed operation. For example:

mysql> SELECT EVENT_NAME, WORK_COMPLETED, WORK_ESTIMATED
       FROM performance_schema.events_stages_history;
+------------------------------------------------------+----------------+----------------+
| EVENT_NAME                                           | WORK_COMPLETED | WORK_ESTIMATED |
+------------------------------------------------------+----------------+----------------+
| stage/innodb/alter table (read PK and internal sort) |            886 |           1213 |
| stage/innodb/alter table (flush)                     |           1213 |           1213 |
| stage/innodb/alter table (log apply table)           |           1597 |           1597 |
| stage/innodb/alter table (end)                       |           1597 |           1597 |
| stage/innodb/alter table (log apply table)           |           1981 |           1981 |
+------------------------------------------------------+----------------+----------------+
5 rows in set (0.00 sec)

如上所示，WORK_ESTIMATED 的值在 ALTER TABLE 处理过程中进行了修改。初始阶段完成后的预计工作量为 1213。当 ALTER TABLE 处理完成时，WORK_ESTIMATED 被设置为实际值，即 1981。As shown above, the WORK_ESTIMATED value was revised during ALTER TABLE processing. The estimated work after completion of the initial stage is 1213. When ALTER TABLE processing completed, WORK_ESTIMATED was set to the actual value, which is 1981.