回滚事务 · k8s原理与实践

[TOC] # 回滚事务使用`ROLLBACK`语句回滚事务。回滚一个事务指将事务的修改全部撤销。可以回滚当前整个未提交的事务，也可以回滚到事务中任意一个保存点。如果要回滚到某个保存点，必须结合使用`ROLLBACK`和`TO SAVEPOINT`语句。其中： * 如果回滚整个事务，则： * 事务会结束 * 所有的修改会被丢弃 * 清除所有保存点 * 释放事务持有的所有锁 * 如果回滚到某个保存点，则： * 事务不会结束 * 保存点之前的修改被保留，保存点之后的修改被丢弃 * 清除保存点之后的保存点（不包括保存点自身） * 释放保存点之后事务持有的所有锁示例如下：回滚事务的全部修改： ~~~ obclient> SELECT * FROM t_insert; +----+------+-------+---------------------+ | ID | NAME | VALUE | GMT_CREATE | +----+------+-------+---------------------+ | 1 | CN | 10001 | 2020-04-02 17:52:31 | | 2 | US | 10002 | 2020-04-02 17:52:38 | | 3 | EN | 10003 | 2020-04-02 17:52:38 | +----+------+-------+---------------------+ 3 rows in set (0.00 sec) obclient> INSERT INTO t_insert(id, name, value) VALUES(4,'JP',10004); Query OK, 1 row affected (0.00 sec) obclient> INSERT INTO t_insert(id, name, value) VALUES(5,'FR',10005),(6,'RU',10006); Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 obclient> SELECT * FROM t_insert; +----+------+-------+---------------------+ | ID | NAME | VALUE | GMT_CREATE | +----+------+-------+---------------------+ | 1 | CN | 10001 | 2020-04-02 17:52:31 | | 2 | US | 10002 | 2020-04-02 17:52:38 | | 3 | EN | 10003 | 2020-04-02 17:52:38 | | 4 | JP | 10004 | 2020-04-02 17:53:34 | | 5 | FR | 10005 | 2020-04-02 17:54:53 | | 6 | RU | 10006 | 2020-04-02 17:54:53 | +----+------+-------+---------------------+ 6 rows in set (0.00 sec) obclient> ROLLBACK; Query OK, 0 rows affected (0.00 sec) obclient> SELECT * FROM t_insert; +----+------+-------+---------------------+ | ID | NAME | VALUE | GMT_CREATE | +----+------+-------+---------------------+ | 1 | CN | 10001 | 2020-04-02 17:52:31 | | 2 | US | 10002 | 2020-04-02 17:52:38 | | 3 | EN | 10003 | 2020-04-02 17:52:38 | +----+------+-------+---------------------+ 3 rows in set (0.00 sec) ~~~