1·I find it a bad practice too, for me it just makes code more verbose with all these useless unsets.
我也觉得不好的实践，对我来说，这就使得代码更详细的所有这些无用的附件。
2·After completing the alter operation transaction, the server unsets the alter mode (if alter mode was set as part of the same transaction).
在完成alter操作事务之后，服务器关闭alter模式(如果在同一个事务中打开了alter模式)。