MySQL找出锁等待

Posted 2020-09-01 moss_tan_jun

1.服务器级别的锁等待

可以通过show processlist看到等待锁的线程id，但是无法知道究竟哪个线程持有锁

可以通过mysqladmin debug

相关等待锁的线程以及谁持有锁可以在错误日志中找到

 

#以下是innodb存储引擎中锁等待以及哪个线程持有锁的查找sql
SELECT r.trx_id AS waiting_trx_id, r.trx_mysql_thread_id AS waiting_thread, TIMESTAMPDIFF(SECOND, r.trx_wait_started, CURRENT_TIMESTAMP) AS wait_time, r.trx_query AS waiting_query, l.lock_table AS waiting_table_lock, b.trx_id AS blocking_trx_id, b.trx_mysql_thread_id AS blocking_thread, SUBSTRING(p.host,1, INSTR(p.host, ‘:‘) -1) AS blocking_host, SUBSTRING(p.host, INSTR(p.host, ‘:‘) +1) AS block_port, IF(p.command="Sleep",p.time,0) AS idle_in_trx, b.trx_query AS blcoking_query
FROM information_schema.innodb_lock_waits AS w
INNER JOIN information_schema.innodb_trx AS b ON b.trx_id=w.blocking_trx_id
INNER JOIN information_schema.innodb_trx AS r ON r.trx_id = w.requesting_trx_id
INNER JOIN information_schema.innodb_locks AS l ON w.requested_lock_id = l.lock_id
LEFT JOIN information_schema.processlist AS p ON p.id = b.trx_mysql_thread_id
ORDER BY wait_time DESC;

#下面查询显示存储引擎层有多少查询被哪些线程阻塞
SELECT CONCAT(‘thread ‘, b.trx_mysql_thread_id, ‘ from ‘,p.host) AS who_blocks, IF (p.command = "Sleep",p.time, 0) AS idle_in_trx, MAX(TIMESTAMPDIFF(SECOND,r.trx_wait_started, NOW())) AS max_wait_time, COUNT(*) AS num_waiters
FROM information_schema.innodb_lock_waits AS w
INNER JOIN information_schema.innodb_trx AS b ON b.trx_id = w.blocking_trx_id
INNER JOIN information_schema.innodb_trx AS r ON r.trx_id = w.requesting_trx_id
LEFT JOIN information_schema.processlist AS p ON p.id = b.trx_mysql_thread_id
GROUP BY who_blocks
ORDER BY num_waiters DESC;