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

测试数据：CREATE TABLE`tb4001` (

`id`bigint(20) NOT NULLAUTO_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';

STARTTRANSACTION;SELECT @@GLOBAL.tx_isolation, @@SESSION.tx_isolation;update tb4001 set c2=777 where c1=7;

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

会话2：SET SESSION tx_isolation='READ-COMMITTED';

STARTTRANSACTION;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';

STARTTRANSACTION;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 tablesin use 1, locked 1LOCK WAIT3 lock struct(s), heap size 1136, 3row lock(s)

MySQL thread id53, OS thread handle 140674620851968, query id 1331 127.0.0.1admin updatingdelete 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 10606lock_mode X waiting

Record lock, heap no11 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

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