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MySQL Transaction--RC事务隔离级别下加锁测试

==============================================================================
非索引列更新

在读提交的事务隔离级别下，在非索引列上进行更新和删除会对修改行的主键索引上加行锁。
如果更新或删除条件为c3=4且c3列上没有索引则：
1、阻止其他会话删除表中任意行数据
2、允许其他会话插入任意记录，包括允许插入c3=4的记录
3、阻止其他会话更新c3=4的记录(主键上有X排他锁)
4、允许其他会话更新c3<>4的记录，包括允许将c3<>4的记录更新为c3=4的记录。


在读提交事务隔离级别下进行更新和删除操作，存储引擎层会对扫描到的记录加X排他锁，但MySQL Server层对此进行优化，将不满足条件记录上的锁进行释放。

##=========================================##
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：RC
会话1：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=777 where c3=7;

##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
insert into tb4001(c1,c2,c3) values(9,9,9);

会话2未被阻塞成功执行


##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
insert into tb4001(c1,c2,c3) values(9,9,7);

会话2未被阻塞成功执行
##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=888 where c3=8;

会话2未被阻塞成功执行

##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c3=7 where c3=8;
会话2未被阻塞成功执行
##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
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 10596 lock_mode X locks rec but not gap waiting
Record lock, heap no 8 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 8; hex 8000000000000003; asc         ;;
 1: len 6; hex 00000000294f; asc     )O;;
 2: len 7; hex 26000000391afe; asc &   9  ;;
 3: len 4; hex 80000007; asc     ;;
 4: len 3; hex 373737; asc 777;;
 5: len 4; hex 80000007; asc     ;;

------------------
---TRANSACTION 10575, ACTIVE 1702 sec
2 lock struct(s), heap size 1136, 1 row lock(s), undo log entries 1
MySQL thread id 52, OS thread handle 140674621650688, query id 1245 127.0.0.1 admin

##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
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 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 10580 lock_mode X locks rec but not gap waiting
Record lock, heap no 8 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 8; hex 8000000000000003; asc         ;;
 1: len 6; hex 00000000294f; asc     )O;;
 2: len 7; hex 26000000391afe; asc &   9  ;;
 3: len 4; hex 80000007; asc     ;;
 4: len 3; hex 373737; asc 777;;
 5: len 4; hex 80000007; asc     ;;

------------------
---TRANSACTION 10575, ACTIVE 232 sec
2 lock struct(s), heap size 1136, 1 row lock(s), undo log entries 1
MySQL thread id 52, OS thread handle 140674621650688, query id 1245 127.0.0.1 admin


##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
delete from  tb4001 where c3=2;

##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 10589 lock_mode X locks rec but not gap waiting
Record lock, heap no 8 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 8; hex 8000000000000003; asc         ;;
 1: len 6; hex 00000000294f; asc     )O;;
 2: len 7; hex 26000000391afe; asc &   9  ;;
 3: len 4; hex 80000007; asc     ;;
 4: len 3; hex 373737; asc 777;;
 5: len 4; hex 80000007; asc     ;;

------------------
---TRANSACTION 10575, ACTIVE 493 sec
2 lock struct(s), heap size 1136, 1 row lock(s), undo log entries 1
MySQL thread id 52, OS thread handle 140674621650688, query id 1245 127.0.0.1 admin

##=========================================##

View Code

==============================================================================

非唯一索引更新

在读提交的事务隔离级别下，按照非主键非唯一索引进行更新和删除，会对满足条件的行加行锁

如果更新或删除条件为c1=4且c1列上有非唯一索引则：
1、阻止其他会话修改删除c1=4的记录
2、允许其他会话插入任意记录，且允许插入c1=4的记录
3、允许其他会话更新c1<>4的任意记录，且允许将记录修改为c1=4的记录
4、允许其他会话删除c1<>4的任意记录

##=========================================##
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：RC
会话1：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=777 where c1=7;

##=========================================##
会话2:
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
insert into tb4001(c1,c2,c3) values(9,9,9);

会话2未被阻塞成功执行

##=========================================##
会话2:
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
insert into tb4001(c1,c2,c3) values(7,7,7);


会话2未被阻塞成功执行

##=========================================##
会话2:
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
delete from  tb4001 where c1=8;

会话2未被阻塞成功执行

##=========================================##
会话2:
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=888 where c1=8;
会话2未被阻塞成功执行

##=========================================##
会话2:
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c1=7 where c1=8;
会话2未被阻塞成功执行


##=========================================##
会话2:
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
delete from  tb4001 where c1=4;
会话2未被阻塞成功执行

##=========================================##

View Code

==============================================================================

非唯一索引+条件更新

在读提交事务隔离级别下，按照对非唯一索引列进行更新，会对扫描到的所有索引记录进行更新，无论该记录是否满足WHERE中的其他条件

##=========================================##
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(4,4,44);
insert into tb4001(c1,c2,c3) values(7,7,7);
insert into tb4001(c1,c2,c3) values(8,8,8);


##=========================================##
##会话1：
##事务隔离级别：RC
会话1：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=444 where c1=4 and c3=4;

##=========================================##
##会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=444 where c1=4 and c3=44;

会话2未被阻塞成功执行
##执行结果：会话2被阻塞
---TRANSACTION 10784, ACTIVE 13 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 2 lock struct(s), heap size 1136, 1 row lock(s)
MySQL thread id 76, OS thread handle 140674621384448, query id 1662 127.0.0.1 admin updating
update tb4001 set c2=444 where c1=4 and c3=44
------- TRX HAS BEEN WAITING 13 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 79 page no 4 n bits 72 index idx_c1 of table `test1`.`tb4001` trx id 10784 lock_mode X locks rec but not gap waiting
Record lock, heap no 3 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 80000004; asc     ;;
 1: len 8; hex 8000000000000002; asc         ;;

------------------
---TRANSACTION 10783, ACTIVE 21 sec
3 lock struct(s), heap size 1136, 2 row lock(s), undo log entries 1
MySQL thread id 75, OS thread handle 140674621916928, query id 1658 127.0.0.1 admin

##=========================================##

View Code

==============================================================================

按照非唯一组合索引更新

假设表TB1上有列C1和C2，有索引IDC_C1_C2(C1,C2)
在读提交事务隔离级别下,会话1按照C1=3 AND C2=4进行更新，则：
1、会话2按照C1=3 AND C2=4进行更新,更新操作被阻塞
2、会话2按照C1=3 AND C2=M(M<>4)进行更新,更新操作不会被阻塞

##=========================================##
##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_c3` (`c1`,`c3`)
) 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(4,4,44);
insert into tb4001(c1,c2,c3) values(7,7,7);
insert into tb4001(c1,c2,c3) values(8,8,8);

##=========================================##
##会话1：
##事务隔离级别：RC
会话1：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=444 where c1=4 and c3=4;

##=========================================##
##会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=444 where c1=4 and c3=44;

会话2未被阻塞成功执行

##=========================================##

View Code

==============================================================================

按照唯一索引更新

在读提交的事务隔离级别下，在唯一索引列上进行更新和删除在唯一索引的索引行上加排他锁。
如果更新或删除条件为c1=7且c1列上存在唯一索引则：
1、阻止其他会话删除和修改c1=7的记录
2、阻止其他会话插入c1=7的记录
3、允许其他会话插入删除修改c1<>7的记录，但不允许将记录修改为c1=7的记录
以上限制通过在唯一索引的索引记录上加排他锁X来实现，不会生产GAP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`),
  UNIQUE 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：RC
会话1：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=777 where c1=7;

##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
insert into tb4001(c1,c2,c3) values(6,6,6);

会话2未被阻塞成功执行


##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
insert into tb4001(c1,c2,c3) values(7,7,7);

##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

mysql tables in use 1, locked 1
LOCK WAIT 3 lock struct(s), heap size 1136, 3 row lock(s)
MySQL thread id 53, OS thread handle 140674620851968, query id 1331 127.0.0.1 admin updating
delete from  tb4001 where c3=8
------- 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 10606 lock_mode X waiting
Record lock, heap no 11 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 8; hex 8000000000000003; asc         ;;
 1: len 6; hex 000000002966; asc     )f;;
 2: len 7; hex 34000000270908; asc 4   '  ;;
 3: len 4; hex 80000007; asc     ;;
 4: len 3; hex 373737; asc 777;;
 5: len 4; hex 80000007; asc     ;;

------------------
---TRANSACTION 10598, ACTIVE 567 sec
4 lock struct(s), heap size 1136, 3 row lock(s), undo log entries 1
MySQL thread id 52, OS thread handle 140674621650688, query id 1306 127.0.0.1 admin

##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c2=888 where c1=8;

会话2未被阻塞成功执行

##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
update tb4001 set c1=7 where c1=8;

会话2未被阻塞成功执行
##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
---TRANSACTION 10686, ACTIVE 14 sec updating or deleting
mysql tables in use 1, locked 1
LOCK WAIT 4 lock struct(s), heap size 1136, 4 row lock(s), undo log entries 1
MySQL thread id 53, OS thread handle 140674620851968, query id 1480 127.0.0.1 admin updating
update tb4001 set c1=7 where c1=8
------- TRX HAS BEEN WAITING 7 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 76 page no 4 n bits 72 index idx_c1 of table `test1`.`tb4001` trx id 10686 lock mode S waiting
Record lock, heap no 4 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 80000007; asc     ;;
 1: len 8; hex 8000000000000003; asc         ;;

------------------
---TRANSACTION 10675, ACTIVE 265 sec
3 lock struct(s), heap size 1136, 2 row lock(s), undo log entries 1
MySQL thread id 52, OS thread handle 140674621650688, query id 1450 127.0.0.1 admin

##=========================================##
会话2：
SET SESSION tx_isolation='READ-COMMITTED';
START TRANSACTION;
SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;
delete from tb4001 where c1=8;

会话2未被阻塞成功执行

##=========================================##

View Code

查看全文

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原文地址：https://www.cnblogs.com/gaogao67/p/10411115.html

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