Question

I have an MySQL InnoDB lock that is preventing a user from logging in. I don’t care about the cause of this lock at the moment – I just need to clear the lock without restarting the database. Killing the query process does nothing FYI. Any suggestions? Thanks.

Answer 1

Here is how I wound up solving the problem:

mysql> show engine innodb status\G
*************************** 1. row ***************************
  Type: InnoDB
  Name: 
Status: 
=====================================
120710 18:05:37 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 37 seconds
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 208374, signal count 196902
Mutex spin waits 0, rounds 39211638, OS waits 80663
RW-shared spins 588505, OS waits 68505; RW-excl spins 3204502, OS waits 53586
------------
TRANSACTIONS
------------
Trx id counter 1 3626791829
Purge done for trx's n:o < 1 3625948819 undo n:o < 0 0
History list length 6754
LIST OF TRANSACTIONS FOR EACH SESSION:
...
---TRANSACTION 1 3625948818, ACTIVE 2892 sec, process no 1981, OS thread id 140020625811200
2 lock struct(s), heap size 368, 1 row lock(s), undo log entries 1

>>>>> MySQL thread id 14982, query id 232584561 localhost dbuser

Trx read view will not see trx with id >= 1 3625948819, sees < 1 3625948817

mysql> kill 14982;
Query OK, 0 rows affected (0.00 sec)

Note that the line with the >>>>> is where the MySQL thread ID is defined – it is this thread that should be killed.

Please see this post as well – very useful.