MySQL5.7如何查询InnoDB锁表
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InnoDB INFORMATION_SCHEMA 里有三张表可以用来监控和诊断锁的问题。
INNODB_TRX
包含正在InnoDB里执行的每个事务的相关信息，包括事务是否在等待锁，事务的开始时间和事务正在执行的SQL语句。
INNODB_LOCKS
记录InnoDB里每个正在等待另一个事务释放锁(INNODB_TRX.TRX_STATE='LOCK WAIT')的事务的相关信息，这些事务被“blocking lock request”事件阻塞，这些锁的请求为被另一个事务占用的行锁或表锁。
等待或阻塞的事务不能进行，直到占有锁的事务提交或回滚。这张表记录事务请求的锁，占有锁的事务信息，占有锁的事务的状态('RUNNING', 'LOCK WAIT', 'ROLLING BACK' or 'COMMITTING')，占有锁的模式(read vs. write, shared vs. exclusive)。
INNODB_LOCK_WAITS
记录哪些事务在等待锁以及等待的锁的类型，REQUESTED_LOCK_ID代表事务请求的锁的ID，BLOCKING_LOCK_ID代表占有锁的ID。
事务1
mysql> BEGIN;
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT MSISDN FROM t50 FOR UPDATE;
+----------------+
| MSISDN |
+----------------+
| +3301000000011 |
| +3301000000013 |
| +3301000000015 |
| +3301000000015 |
| +3301000000017 |
| +3301000000019 |
+----------------+
6 rows in set (0.00 sec)
mysql> SELECT SLEEP(1000);
事务2
mysql> SELECT IMEI FROM t50 FOR UPDATE;
事务3
mysql> SELECT IMSI FROM t50 FOR UPDATE;
再开一个会话，查看线程信息
mysql> show processlist;
+----+------+-----------+------+---------+------+--------------+---------------------------------+-----------+---------------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined |
+----+------+-----------+------+---------+------+--------------+---------------------------------+-----------+---------------+
| 70 | root | localhost | test | Query | 8 | Sending data | SELECT IMEI FROM t50 FOR UPDATE | 0 | 0 |
| 71 | root | localhost | test | Query | 310 | User sleep | SELECT SLEEP(1000) | 0 | 0 |
| 72 | root | localhost | test | Query | 6 | Sending data | SELECT IMSI FROM t50 FOR UPDATE | 0 | 0 |
| 73 | root | localhost | test | Query | 0 | init | show processlist | 0 | 0 |
+----+------+-----------+------+---------+------+--------------+---------------------------------+-----------+---------------+
4 rows in set (0.03 sec)
查看锁的信息
mysql> SELECT r.trx_id waiting_trx_id,
-> r.trx_mysql_thread_id waiting_thread,
-> r.trx_query waiting_query,
-> b.trx_id blocking_trx_id,
-> b.trx_mysql_thread_id blocking_thread,
-> b.trx_query blocking_query
-> FROM information_schema.innodb_lock_waits w
-> INNER JOIN information_schema.innodb_trx b ON
-> b.trx_id = w.blocking_trx_id
-> INNER JOIN information_schema.innodb_trx r ON
-> r.trx_id = w.requesting_trx_id;
+----------------+----------------+---------------------------------+-----------------+-----------------+---------------------------------+
| waiting_trx_id | waiting_thread | waiting_query | blocking_trx_id | blocking_thread | blocking_query |
+----------------+----------------+---------------------------------+-----------------+-----------------+---------------------------------+
| 6288648 | 72 | SELECT IMSI FROM t50 FOR UPDATE | 6288647 | 70 | SELECT IMEI FROM t50 FOR UPDATE |
| 6288648 | 72 | SELECT IMSI FROM t50 FOR UPDATE | 6288638 | 71 | SELECT SLEEP(1000) |
| 6288647 | 70 | SELECT IMEI FROM t50 FOR UPDATE | 6288638 | 71 | SELECT SLEEP(1000) |
+----------------+----------------+---------------------------------+-----------------+-----------------+---------------------------------+
3 rows in set (0.00 sec)
可以看到，最初执行SQL的线程是 71，线程 70 等待线程 71 ，线程 72 在等待线程 70、71
mysql> select * from information_schema.INNODB_LOCKS;
+----------------+-------------+-----------+-----------+--------------+-----------------+------------+-----------+----------+----------------+
| lock_id | lock_trx_id | lock_mode | lock_type | lock_table | lock_index | lock_space | lock_page | lock_rec | lock_data |
+----------------+-------------+-----------+-----------+--------------+-----------------+------------+-----------+----------+----------------+
| 6288651:78:3:2 | 6288651 | X | RECORD | `test`.`t50` | GEN_CLUST_INDEX | 78 | 3 | 2 | 0x000000000607 |
| 6288650:78:3:2 | 6288650 | X | RECORD | `test`.`t50` | GEN_CLUST_INDEX | 78 | 3 | 2 | 0x000000000607 |
| 6288638:78:3:2 | 6288638 | X | RECORD | `test`.`t50` | GEN_CLUST_INDEX | 78 | 3 | 2 | 0x000000000607 |
+----------------+-------------+-----------+-----------+--------------+-----------------+------------+-----------+----------+----------------+
3 rows in set (0.00 sec)
mysql> select trx_id,trx_state,trx_started,trx_requested_lock_id,trx_wait_started,trx_mysql_thread_id,trx_query from information_schema.INNODB_TRX;
+---------+-----------+---------------------+-----------------------+---------------------+---------------------+---------------------------------+
| trx_id | trx_state | trx_started | trx_requested_lock_id | trx_wait_started | trx_mysql_thread_id | trx_query |
+---------+-----------+---------------------+-----------------------+---------------------+---------------------+---------------------------------+
| 6288669 | LOCK WAIT | 2016-09-05 14:14:28 | 6288669:78:3:2 | 2016-09-05 14:14:28 | 72 | SELECT IMSI FROM t50 FOR UPDATE |
| 6288668 | LOCK WAIT | 2016-09-05 14:14:26 | 6288668:78:3:2 | 2016-09-05 14:14:26 | 70 | SELECT IMEI FROM t50 FOR UPDATE |
| 6288638 | RUNNING | 2016-09-05 11:41:59 | NULL | NULL | 71 | SELECT SLEEP(1000) |
+---------+-----------+---------------------+-----------------------+---------------------+---------------------+---------------------------------+
3 rows in set (0.00 sec)
mysql> select * from information_schema.INNODB_LOCK_WAITS;
+-------------------+-------------------+-----------------+------------------+
| requesting_trx_id | requested_lock_id | blocking_trx_id | blocking_lock_id |
+-------------------+-------------------+-----------------+------------------+
| 6288671 | 6288671:78:3:2 | 6288670 | 6288670:78:3:2 |
| 6288671 | 6288671:78:3:2 | 6288638 | 6288638:78:3:2 |
| 6288670 | 6288670:78:3:2 | 6288638 | 6288638:78:3:2 |
+-------------------+-------------------+-----------------+------------------+
3 rows in set (0.00 sec)
检查Innodb_row_lock状态变量来分析系统上的行锁的争夺情况
mysql> show global status like '%innodb%row%lock%';
+-------------------------------+-------+
| Variable_name | Value |
+-------------------------------+-------+
| Innodb_row_lock_current_waits | 0 |
| Innodb_current_row_locks | 0 |
| Innodb_row_lock_time | 0 |
| Innodb_row_lock_time_avg | 0 |
| Innodb_row_lock_time_max | 0 |
| Innodb_row_lock_waits | 0 |
+-------------------------------+-------+
6 rows in set (0.00 sec)
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