mysql innodb 死锁分析

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mysql Ver 14.14 Distrib 5.7.16, for linux-glibc2.5 (x86_64) using EditLine wrapper #mysql版本 5.7.16

Connection id: 10042
Current database: china9129
Current user: root@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.7.16-log MySQL Community Server (GPL)
Protocol version: 10
Connection: Localhost via UNIX socket
Server characterset: utf8
Db characterset: utf8
Client characterset: utf8
Conn. characterset: utf8
UNIX socket: /data/mysql/mysql9129/sock/mysql9129.sock
Uptime: 4 days 6 hours 2 min 31 sec


Threads: 4 Questions: 31133 Slow queries: 0 Opens: 254 Flush tables: 3 Open tables: 58 Queries per second avg: 0.084

SESSION 1:
"root@localhost:mysql9129.sock [(none)]>set global TRANSACTION ISOLATION LEVEL REPEATABLE READ;
"root@localhost:mysql9129.sock [(none)]>select @@tx_isolation;
+-----------------+
| @@tx_isolation |
+-----------------+
| REPEATABLE-READ |
+-----------------+
1 row in set (0.00 sec)

"root@localhost:mysql9129.sock [china9129]>show create table t100;
+-------+----------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+----------------------------------------------------------------------------------------------------------+
| t100 | CREATE TABLE `t100` (
  `id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+-------+----------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

"root@localhost:mysql9129.sock [china9129]>select * from t100;
+-----+
| id |
+-----+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 111 |
+-----+

"root@localhost:mysql9129.sock [china9129]>begin;
Query OK, 0 rows affected (0.00 sec)

"root@localhost:mysql9129.sock [china9129]>select * from t100 where id=5 for update;
+----+
| id |
+----+
| 5 |
+----+
1 row in set (0.00 sec)

"root@localhost:mysql9129.sock [china9129]>delete from t100 where id =3;
Query OK, 1 row affected (3.62 sec)

==========================================================================================================
SESSION 2:

"root@localhost:mysql9129.sock [(none)]>begin;
Query OK, 0 rows affected (0.00 sec)

"root@localhost:mysql9129.sock [(none)]>use china9129;
Database changed
"root@localhost:mysql9129.sock [china9129]>select * from t100 where id=3 for update;
+----+
| id |
+----+
| 3 |
+----+
1 row in set (0.00 sec)

"root@localhost:mysql9129.sock [china9129]>delete from t100 where id =5;
ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction


#查看死锁信息
"root@localhost:mysql9129.sock [china9129]>show engine innodb status \G
*************************** 1. row ***************************
  Type: InnoDB
  Name:
Status:
=====================================
2016-12-20 21:57:45 0x7fa0bffff700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 24 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 1133 srv_active, 0 srv_shutdown, 362529 srv_idle
srv_master_thread log flush and writes: 363662
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 4540
OS WAIT ARRAY INFO: signal count 5766
RW-shared spins 0, rounds 4683, OS waits 474
RW-excl spins 0, rounds 134731, OS waits 1327
RW-sx spins 6332, rounds 138603, OS waits 2382
Spin rounds per wait: 4683.00 RW-shared, 134731.00 RW-excl, 21.89 RW-sx
------------------------
LATEST DETECTED DEADLOCK #监测出最近的死锁信息
------------------------
2016-12-20 21:56:29 0x7fa0bffff700
*** (1) TRANSACTION: #第一个事物
TRANSACTION 13899, ACTIVE 51 sec starting index read #事物id 13899，活跃了51秒
mysql tables in use 1, locked 1 #mysql有一个表在使用，一个表被锁住
LOCK WAIT 3 lock struct(s), heap size 1136, 2 row lock(s) #有3个锁链表，内存中堆的大小1136, 两行记录被锁定
MySQL thread id 10041, OS thread handle 140330009478912, query id 31128 localhost root updating
#mysql线程id 10041, query id 31128, localhost root用户执行update操作
delete from t100 where id =3 #执行了这个SQL语句的时候，发生了锁等待
*** (1) WAITING FOR THIS LOCK TO BE GRANTED: #等待这个锁被释放
RECORD LOCKS space id 74 page no 3 n bits 80 index PRIMARY of table `china9129`.`t100` trx id 13899 lock_mode X locks rec but not gap waiting
#类型：行锁，等待在t100的主键上 page num 3，加一个X锁(not gap waiting)，锁住80 bits。
Record lock, heap no 5 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
0: len 4; hex 80000003; asc ;;
1: len 6; hex 00000000363b; asc 6;;;
2: len 7; hex c7000001660110; asc f ;;


*** (2) TRANSACTION:#第二个事物
TRANSACTION 13900, ACTIVE 31 sec starting index read #事物id 13900，活跃了31秒
mysql tables in use 1, locked 1 #mysql有一个表在使用，一个表被锁住
3 lock struct(s), heap size 1136, 2 row lock(s) #有3个锁链表，内存中堆的大小1136, 两行记录被锁定
MySQL thread id 10042, OS thread handle 140328392718080, query id 31129 localhost root updating
#mysql线程id 10042, query id 31129, localhost root用户执行update操作
delete from t100 where id =5 #执行了这个SQL语句的时候，发生了锁等待
*** (2) HOLDS THE LOCK(S): #事物 13900 持有的锁
RECORD LOCKS space id 74 page no 3 n bits 80 index PRIMARY of table `china9129`.`t100` trx id 13900 lock_mode X locks rec but not gap
#类型：行锁，事物 id 13900，在t100的主键上 page num 3，加一个X锁(not gap 没有间隙锁)，锁住80 bits
Record lock, heap no 5 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
0: len 4; hex 80000003; asc ;;
1: len 6; hex 00000000363b; asc 6;;;
2: len 7; hex c7000001660110; asc f ;;


*** (2) WAITING FOR THIS LOCK TO BE GRANTED: #当事物2在执行delete from t100 where id =5的时候，发生锁等待
RECORD LOCKS space id 74 page no 3 n bits 80 index PRIMARY of table `china9129`.`t100` trx id 13900 lock_mode X locks rec but not gap waiting
#类型：行锁，等待在t100的主键上 page num 3，加一个X锁(not gap waiting 没有间隙锁)，锁住80 bits。
Record lock, heap no 7 PHYSICAL RECORD: n_fields 3; compact format; info bits 0
0: len 4; hex 80000005; asc ;;
1: len 6; hex 00000000363d; asc 6=;;
2: len 7; hex c90000014c0110; asc L ;;


*** WE ROLL BACK TRANSACTION (2)
#事物2，TRANSACTION 13900被回滚了。报错信息：ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction
------------
TRANSACTIONS
------------
Trx id counter 13905
Purge done for trx's n:o < 13905 undo n:o < 0 state: running but idle
History list length 568
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 421807334705888, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 13899, ACTIVE 127 sec
3 lock struct(s), heap size 1136, 2 row lock(s), undo log entries 1
MySQL thread id 10041, OS thread handle 140330009478912, query id 31128 localhost root cleaning up
-------

备注:
(1) 在MySQL中，行级锁并不是直接锁记录，而是锁索引。索引分为主键索引和非主键索引两种，如果一条sql语句操作了主键索引，MySQL就会锁定这条主键索引；如果一 条语句操作了非主键索引，MySQL会先锁定该非主键索引，再锁定相关的主键索引。
    在UPDATE、DELETE操作时，MySQL不仅锁定WHERE条件扫描过的所有索引记录，而且会锁定相邻的键值，即所谓的next-key locking
(2) 把死锁信息写入到error.log。
    set global innodb_print_all_deadlocks = 1;