查找MySQL线程中死锁的ID的方法

如果遇到死锁了，怎么解决呢？找到原始的锁ID，然后KILL掉一直持有的那个线程就可以了，但是众多线程，可怎么找到引起死锁的线程ID呢？ MySQL 发展到现在，已经非常强大了，这个问题很好解决。直接从数据字典连查找。

我们来演示下。

线程A，我们用来锁定某些记录，假设这个线程一直没提交，或者忘掉提交了。那么就一直存在，但是数据里面显示的只是SLEEP状态。

mysql> set @@autocommit=0;
 
Query OK, 0 rows affected (0.00 sec)
 
mysql> use test;
 
Reading table information for completion of table and column names
 
You can turn off this feature to get a quicker startup with -A
 
Database changed
 
mysql> show tables;
 
+—————-+
 
| Tables_in_test |
 
+—————-+
 
| demo_test   |
 
| t3       |
 
+—————-+
 
2 rows in set (0.00 sec)
 
mysql> select * from t3;
 
+—-+——–+——–+————+—-+—-+—-+
 
| id | fname | lname | birthday  | c1 | c2 | c3 |
 
+—-+——–+——–+————+—-+—-+—-+
 
| 19 | lily19 | lucy19 | 2013-04-18 | 19 | 0 | 0 |
 
| 20 | lily20 | lucy20 | 2013-03-13 | 20 | 0 | 0 |
 
+—-+——–+——–+————+—-+—-+—-+
 
2 rows in set (0.00 sec)
 
mysql> update t3 set birthday = '2022-02-23' where id = 19;
 
Query OK, 1 row affected (0.00 sec)
 
Rows matched: 1 Changed: 1 Warnings: 0
 
mysql> select connection_id();
 
+—————–+
 
| connection_id() |
 
+—————–+
 
|       16 |
 
+—————–+
 
1 row in set (0.00 sec)
 
mysql>

线程B，我们用来进行普通的更新，但是遇到问题了，此时不知道是哪个线程把这行记录给锁定了？

mysql> use test;
 
Reading table information for completion of table and column names
 
You can turn off this feature to get a quicker startup with -A
 
Database changed
 
mysql> select @@autocommit;
 
+————–+
 
| @@autocommit |
 
+————–+
 
|      1 |
 
+————–+
 
1 row in set (0.00 sec)
 
mysql> update t3 set birthday='2018-01-03' where id = 19;
 
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
 
mysql> select connection_id();
 
+—————–+
 
| connection_id() |
 
+—————–+
 
|       17 |
 
+—————–+
 
1 row in set (0.00 sec)
 
mysql> show processlist;
 
+—-+——+———–+——+———+——+——-+——————+
 
| Id | User | Host   | db  | Command | Time | State | Info       |
 
+—-+——+———–+——+———+——+——-+——————+
 
| 10 | root | localhost | NULL | Sleep  | 1540 |    | NULL       |
 
| 11 | root | localhost | NULL | Sleep  | 722 |    | NULL       |
 
| 16 | root | localhost | test | Sleep  | 424 |    | NULL       |
 
| 17 | root | localhost | test | Query  |  0 | init | show processlist |
 
| 18 | root | localhost | NULL | Sleep  |  5 |    | NULL       |
 
+—-+——+———–+——+———+——+——-+——————+
 
5 rows in set (0.00 sec)
 
mysql> show engine innodb status\G
 
————
 
TRANSACTIONS
 
————
 
Trx id counter 189327
 
Purge done for trx's n:o < 189323 undo n:o < 0 state: running but idle
 
History list length 343
 
LIST OF TRANSACTIONS FOR EACH SESSION:
 
—TRANSACTION 0, not started
 
MySQL thread id 11, OS thread handle 0x7f70a0c98700, query id 994 localhost root init
 
show engine innodb status
 
—TRANSACTION 189326, ACTIVE 2 sec starting index read
 
mysql tables in use 1, locked 1
 
LOCK WAIT 2 lock struct(s), heap size 376, 1 row lock(s)
 
MySQL thread id 17, OS thread handle 0x7f70a0bd5700, query id 993 localhost root updating
 
update t3 set birthday='2018-01-03' where id = 19
 
——- TRX HAS BEEN WAITING 2 SEC FOR THIS LOCK TO BE GRANTED:
 
RECORD LOCKS space id 529 page no 3 n bits 72 index `PRIMARY` of table `test`.`t3` trx id 189326 lock_mode X waiting
 
Record lock, heap no 2 PHYSICAL RECORD: n_fields 9; compact format; info bits 0
 
0: len 2; hex 3139; asc 19;;
 
1: len 6; hex 00000002e38c; asc    ;;
 
2: len 7; hex 7e00000d2827c9; asc ~  (' ;;
 
3: len 6; hex 6c696c793139; asc lily19;;
 
4: len 6; hex 6c7563793139; asc lucy19;;
 
5: len 3; hex 8fcc57; asc  W;;
 
6: len 4; hex 80000013; asc   ;;
 
7: len 4; hex 80000000; asc   ;;
 
8: len 4; hex 80000000; asc   ;;
 
——————
 
—TRANSACTION 189324, ACTIVE 641 sec
 
2 lock struct(s), heap size 376, 3 row lock(s), undo log entries 1
 
MySQL thread id 16, OS thread handle 0x7f70a0b94700, query id 985 localhost root cleaning up
 
Trx read view will not see trx with id >= 189325, sees < 189325

上面的信息很繁多，也看不清楚到底哪里是哪里。

不过现在，我们只要从数据字典里面拿出来这部分信息就OK了。

mysql> SELECT * FROM information_schema.INNODB_TRX\G
 
*************************** 1. row ***************************
 
          trx_id: 189324
 
        trx_state: RUNNING
 
       trx_started: 2013-04-18 17:48:14
 
  trx_requested_lock_id: NULL
 
     trx_wait_started: NULL
 
        trx_weight: 3
 
   trx_mysql_thread_id: 16
 
        trx_query: NULL
 
   trx_operation_state: NULL
 
    trx_tables_in_use: 0
 
    trx_tables_locked: 0
 
     trx_lock_structs: 2
 
  trx_lock_memory_bytes: 376
 
     trx_rows_locked: 3
 
    trx_rows_modified: 1
 
 trx_concurrency_tickets: 0
 
   trx_isolation_level: REPEATABLE READ
 
    trx_unique_checks: 1
 
  trx_foreign_key_checks: 1
 
trx_last_foreign_key_error: NULL
 
trx_adaptive_hash_latched: 0
 
trx_adaptive_hash_timeout: 10000
 
     trx_is_read_only: 0
 
trx_autocommit_non_locking: 0
 
1 row in set (0.01 sec)
 
mysql>

原来是线程16忘掉COMMIT了。