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:
-
- MySQL thread id 11, OS thread handle 0x7f70a0c98700, query id 994 localhost root init
- show engine innodb status
-
- 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
-
- 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 ;;
-
-
- 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。
本文出自：http://yueliangdao0608.blog.51cto.com/397025/1180917
