mysql 只有几百条数据的update 更新了10s一般是什么问题，我查询了锁表，机器的io都没发现问题

update 语句:
2019-05-13 09:43:37.705 http-nio-8401-exec-3: DEBUG com.ybjdw.order.itemorder.dao.OrderRowMapper.updateByExampleSelective - ==> Preparing: update order_row SET end_date = ?, modify_date = ? WHERE ( item_id = ? )
2019-05-13 09:43:37.706 http-nio-8401-exec-3: DEBUG com.ybjdw.order.itemorder.dao.OrderRowMapper.updateByExampleSelective - ==> Parameters: 2019-05-13 09:43:32.695(Timestamp), 2019-05-13 09:43:32.695(Timestamp), 100001015577113592290000(String)
2019-05-13 09:43:42.696 http-nio-8401-exec-3: DEBUG com.ybjdw.order.itemorder.dao.OrderRowMapper.updateByExampleSelective - <== Updates: 3

item_id 没有索引，表中有601条数据