show create table history;
--------------------------
 CREATE TABLE `foo` (
  `itemid` bigint(20) unsigned NOT NULL,
  `clock` int(11) NOT NULL DEFAULT '0',
  `value` double(16,4) NOT NULL DEFAULT '0.0000',
  `ns` int(11) NOT NULL DEFAULT '0',
  KEY `history_1` (`itemid`,`clock`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

mysql> OPTIMIZE TABLE history;
+----------+----------+----------+-------------------------------------------------------------------+

| Table    | Op       | Msg_type | Msg_text                                                          |

+----------+----------+----------+-------------------------------------------------------------------+

| test.foo | optimize | note     | Table does not support optimize, doing recreate + analyze instead |

| test.foo | optimize | status   | OK                                                                |

+----------+----------+----------+-------------------------------------------------------------------+

这里mysql给的提示是

Note>> Table does not support optimize, doing recreate + analyze instead 
Status>> OK
也就是说 optimize table 对于innodb来说，无法作为a single operation，实际的操作是：

ALTER TABLE test.foo ENGINE=InnoDB;

ANALYZE TABLE test.foo;

MySQL5.7已经推荐对于InnoDB的table使用 alter table table_name engine=innodb;语句的方式来进行表碎片优化。

底层实现的不同，参考：https://dev.mysql.com/doc/refman/5.7/en/optimize-table.html