MySQL innodb_rollback_on_timeout参数对锁的影响

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环境：Server version: 5.6.21-log MySQL Community Server (GPL)

前提提要：

innodb_rollback_on_timeout 是啥作用？
答：事务 B 在锁等待超时后是回滚事务内所有的 statement 还是最后一条语句；
0 表示 rollback 最后一条语句，默认值；有点坑
1 表示回滚事务 B 内所有的 statements；
此参数是只读参数，需在 my.cnf 中配置，并且重启生效；
注意：回滚 statements 后不自动 commit 或 rollback 事务；坑

表结构：

mysql> show create table t12\G;
*************************** 1. row ***************************
Table: t12
Create Table: CREATE TABLE `t12` (
`a` int(10) unsigned NOT NULL AUTO_INCREMENT,
`b` varchar(766) DEFAULT NULL,
`c` int(11) DEFAULT NULL,
PRIMARY KEY (`a`),
KEY `b` (`b`)
) ENGINE=InnoDB AUTO_INCREMENT=16 DEFAULT CHARSET=latin1
row in set (0.00 sec)

实验一：

 参数配置：mysql> show variables like 'innodb_rollback_on_timeout';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| innodb_rollback_on_timeout | ON    |
+----------------------------+-------+
1 row in set (0.00 sec)

mysql> show variables like 'tx_iso%';
+---------------+-----------------+
| Variable_name | Value           |
+---------------+-----------------+
| tx_isolation  | REPEATABLE-READ |
+---------------+-----------------+
1 row in set (0.00 sec)

mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit    | ON    |
+---------------+-------+
1 row in set (0.00 sec)

过程：

MySQL innodb_rollback_on_timeout 参数对锁的影响

实验二：

 参数配置：mysql> show variables like 'innodb_rollback_on_timeout';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| innodb_rollback_on_timeout | OFF   |
+----------------------------+-------+
1 row in set (0.00 sec)

mysql> show variables like 'tx_iso%';
+---------------+-----------------+
| Variable_name | Value           |
+---------------+-----------------+
| tx_isolation  | REPEATABLE-READ |
+---------------+-----------------+
1 row in set (0.00 sec)

mysql> show variables like 'autocommit';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit    | ON    |
+---------------+-------+
1 row in set (0.00 sec)