Shulou(Shulou.com)06/01 Report--

Early in the morning to brush the data, a large number of table structure alter statements, the table will be locked.

Locking tables may be encountered in the use of the database, resulting in timeouts when other processes access the same table. If it is production, you will see a large number of pool kneeling. If you are browsing sql, you should immediately understand what is going on.

Show full processlist

Show which threads are running, view lock table statements, and so on:

The situation of locking the table is like the picture above: waiting for table metadata lock, if it is not in conflict with other things, it will be fine on its own, or it can stop its own sql and it will release the lock. In case of conflict with other things, it can be killed, kill 2292.

Check the table that is being locked and note: I didn't execute this at the time of the accident. I don't know the result. I forget it every time.

Show OPEN TABLES where In_use > 0

View transactions that are being locked

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS

View transactions waiting for locks

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS

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