MySQL Transaction--RR事务隔离级别下加锁测试

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按照非索引列更新

在可重复读的事务隔离级别下，在非索引列上进行更新和删除会对所有数据行进行加锁，阻止其他会话对边进行任何数据的增删改操作。

如果更新或删除条件为c3=4且c3列上没有索引则：
1、不允许其他会话插入任意记录，因为所有记录的主键索引上存在X排他锁，无法申请插入意向X锁（lock_mode X insert intention waiting Record lock）
2、不允许其他会话删除任意记录，因为所有记录的主键索引上存在X排他锁
3、不允许其他会话更新任意记录。因为所有记录的主键索引上存在X排他锁

##=========================================##
测试数据：
CREATE TABLE `tb4001` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `c1` int(11) DEFAULT NULL,
  `c2` varchar(200) DEFAULT NULL,
  `c3` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `idx_c1` (`c1`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

insert into tb4001(c1,c2,c3) values(2,2,2);
insert into tb4001(c1,c2,c3) values(4,4,4);
insert into tb4001(c1,c2,c3) values(7,7,7);
insert into tb4001(c1,c2,c3) values(8,8,8);

##=========================================##
##测试1：在没有索引的列上更新
##事务隔离级别：RR
会话1：
SET SESSION tx_isolation='REPEATABLE-READ';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=777 where c3=7;

##=========================================##
会话2:
SET SESSION tx_isolation='REPEATABLE-READ';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;

insert into tb4001(c1,c2,c3) values(9,9,9);

##执行结果：会话2被阻塞
使用SHOW ENGINE INNODB STATUS \G查看阻塞发生时的锁信息
------- TRX HAS BEEN WAITING 13 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 75 page no 3 n bits 80 index PRIMARY of table `test1`.`tb4001` trx id 10573 lock_mode X insert intention waiting Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
 0: len 8; hex 73757072656d756d; asc supremum;;

------------------
---TRANSACTION 10571, ACTIVE 404 sec
2 lock struct(s), heap size 1136, 5 row lock(s), undo log entries 1
MySQL thread id 52, OS thread handle 140674621650688, query id 1201 127.0.0.1 admin

##=========================================##
会话2:
SET SESSION tx_isolation='REPEATABLE-READ';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;

update tb4001 set c2=888 where c3=8;

##执行结果：会话2被阻塞
使用SHOW ENGINE INNODB STATUS \G查看阻塞发生时的锁信息
------- TRX HAS BEEN WAITING 5 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 75 page no 3 n bits 80 index PRIMARY of table `test1`.`tb4001` trx id 10573 lock_mode X waiting
Record lock, heap no 2 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 8; hex 8000000000000001; asc         ;;
 1: len 6; hex 00000000293c; asc     )<;;
 2: len 7; hex b90000001c0110; asc        ;;
 3: len 4; hex 80000002; asc     ;;
 4: len 1; hex 32; asc 2;;
 5: len 4; hex 80000002; asc     ;;

------------------
---TRANSACTION 10571, ACTIVE 681 sec
2 lock struct(s), heap size 1136, 5 row lock(s), undo log entries 1
MySQL thread id 52, OS thread handle 140674621650688, query id 1201 127.0.0.1 admin


##=========================================##
会话2:
SET SESSION tx_isolation='REPEATABLE-READ';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;

delete from  tb4001 where c3=8;
##执行结果：会话2被阻塞
使用SHOW ENGINE INNODB STATUS \G查看阻塞发生时的锁信息
------- TRX HAS BEEN WAITING 4 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 75 page no 3 n bits 80 index PRIMARY of table `test1`.`tb4001` trx id 10573 lock_mode X waiting
Record lock, heap no 2 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 8; hex 8000000000000001; asc         ;;
 1: len 6; hex 00000000293c; asc     )<;;
 2: len 7; hex b90000001c0110; asc        ;;
 3: len 4; hex 80000002; asc     ;;
 4: len 1; hex 32; asc 2;;
 5: len 4; hex 80000002; asc     ;;

------------------
---TRANSACTION 10571, ACTIVE 790 sec
2 lock struct(s), heap size 1136, 5 row lock(s), undo log entries 1
MySQL thread id 52, OS thread handle 140674621650688, query id 1201 127.0.0.1 admin

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