死锁复现
CREATE TABLE `t` (`id` int(11) NOT NULL,`c` int(11) DEFAULT NULL,`d` int(11) DEFAULT NULL,PRIMARY KEY (`id`),KEY `c` (`c`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;/*Data for the table `t` */insert into `t`(`id`,`c`,`d`) values (0,0,0),(5,5,5),(10,10,10)| 事务1 | 事务2 | |
| T1 | START TRANSACTION ; SELECT * FROM t WHERE id =5 LOCK IN SHARE MODE | |
| T2 | START TRANSACTION ; SELECT * FROM t WHERE id =5 LOCK IN SHARE MODE | |
| T3 | SELECT * FROM t WHERE id =5 FOR UPDATE （阻塞） | |
| T4 | SELECT * FROM t WHERE id =5 FOR UPDATE (死锁) |
死锁分析
- T1事务1加id=5主键索引读锁成功
- T2事务2加id=5主键索引读锁成功
- T3事务1加id=5主键索引写锁阻塞
- T3事务2加id=5主键索引写锁阻塞，进入循环等待，死锁
SHOW ENGINE INNODB STATUS 查看加锁信息
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LATEST DETECTED DEADLOCK
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2024-03-10 15:49:31 0x10bc
*** (1) TRANSACTION:
TRANSACTION 486540, ACTIVE 21 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 4 lock struct(s), heap size 1136, 2 row lock(s)
MySQL thread id 4, OS thread handle 7296, query id 2804 localhost ::1 root statistics
SELECT * FROM t WHERE id =5 for update
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 638 page no 3 n bits 80 index PRIMARY of table `test`.`t` trx id 486540 lock_mode X locks rec but not gap waiting
Record lock, heap no 3 PHYSICAL RECORD: n_fields 5; compact format; info bits 00: len 4; hex 80000005; asc ;;1: len 6; hex 000000046952; asc iR;;2: len 7; hex 4b0000019207d7; asc K ;;3: len 4; hex 80000005; asc ;;4: len 4; hex 80000005; asc ;;*** (2) TRANSACTION:
TRANSACTION 486541, ACTIVE 14 sec starting index read
mysql tables in use 1, locked 1
4 lock struct(s), heap size 1136, 2 row lock(s)
MySQL thread id 5, OS thread handle 4284, query id 2809 localhost ::1 root statistics
SELECT * FROM t WHERE id =5 FOR UPDATE
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 638 page no 3 n bits 80 index PRIMARY of table `test`.`t` trx id 486541 lock mode S locks rec but not gap
Record lock, heap no 3 PHYSICAL RECORD: n_fields 5; compact format; info bits 00: len 4; hex 80000005; asc ;;1: len 6; hex 000000046952; asc iR;;2: len 7; hex 4b0000019207d7; asc K ;;3: len 4; hex 80000005; asc ;;4: len 4; hex 80000005; asc ;;*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 638 page no 3 n bits 80 index PRIMARY of table `test`.`t` trx id 486541 lock_mode X locks rec but not gap waiting
Record lock, heap no 3 PHYSICAL RECORD: n_fields 5; compact format; info bits 00: len 4; hex 80000005; asc ;;1: len 6; hex 000000046952; asc iR;;2: len 7; hex 4b0000019207d7; asc K ;;3: len 4; hex 80000005; asc ;;4: len 4; hex 80000005; asc ;;*** WE ROLL BACK TRANSACTION (2)
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TRANSACTIONS
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