MySQL 查看死锁情况
在使用MySQL数据库时，经常会遇到死锁的情况。死锁是指两个或多个事务互相等待对方释放资源，导致永久阻塞的情况。当发生死锁时，MySQL会自动选择一个事务进行回滚，以解除死锁状态。但是，我们通常需要查看死锁情况，以便定位和解决问题。本文将介绍如何通过MySQL来查看死锁情况，并且提供一些示例代码来帮助理解。
查看死锁情况
在MySQL中，可以通过以下几种方式来查看死锁情况：
-
SHOW ENGINE INNODB STATUS
使用该命令可以查看InnoDB存储引擎的状态信息，包括死锁情况。执行以下SQL语句可以查看InnoDB存储引擎的状态：
SHOW ENGINE INNODB STATUS;执行该命令后，可以查看到一些关于InnoDB存储引擎的信息，其中包括死锁情况。以下是一个示例输出：
------------------------ LATEST DETECTED DEADLOCK ------------------------ 2021-01-01 10:00:00 0x12345678 *** (1) TRANSACTION: TRANSACTION 123456789, ACTIVE 0 sec starting index read mysql tables in use 1, locked 1 LOCK WAIT 3 lock struct(s), heap size 1136, 2 row lock(s) MySQL thread id 1, OS thread handle 0x2aabcde0, query id 123456789 localhost root updating UPDATE table1 SET column1 = 'value1' WHERE id = 1 *** (1) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 123456789 page no 123456789 n bits 120 index `PRIMARY` of table `database`.`table1` trx id 123456789 lock_mode X locks rec but not gap waiting Record lock, heap no 2 PHYSICAL RECORD: n_fields 5; compact format; info bits 0 0: len 4; hex 80000001; asc ;; 1: len 6; hex 0000023abcde; asc ;; 2: len 7; hex 0000023abcde01; asc ;; 3: len 4; hex 80000001; asc ;; 4: len 4; hex 80000001; asc ;; *** (2) TRANSACTION: TRANSACTION 123456788, ACTIVE 0 sec starting index read mysql tables in use 1, locked 1 5 lock struct(s), heap size 1136, 3 row lock(s) MySQL thread id 2, OS thread handle 0x2aabcdf0, query id 123456788 localhost root updating UPDATE table1 SET column1 = 'value2' WHERE id = 2 *** (2) HOLDS THE LOCK(S): RECORD LOCKS space id 123456789 page no 123456789 n bits 120 index `PRIMARY` of table `database`.`table1` trx id 123456788 lock mode S locks rec but not gap Record lock, heap no 3 PHYSICAL RECORD: n_fields 5; compact format; info bits 0 0: len 4; hex 80000002; asc ;; 1: len 6; hex 0000023abcdf; asc ;; 2: len 7; hex 0000023abcdf02; asc ;; 3: len 4; hex 80000002; asc ;; 4: len 4; hex 80000002; asc ;; *** (2) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 123456789 page no 123456789 n bits 120 index `PRIMARY` of table `database`.`table1` trx id 123456788 lock_mode X locks rec but not gap waiting Record lock, heap no 2 PHYSICAL RECORD: n_fields 5; compact format; info bits 0 0: len 4; hex 80000001; asc ;; 1: len 6; hex 0000023abcde; asc ;; 2: len 7; hex 0000023abcde01; asc ;; 3: len 4; hex 80000001; asc ;; 4: len 4; hex 80000001;
