1.伺服器級別的鎖等待
可以通過show processlist看到等待鎖的執行緒id，但是無法知道究竟哪個執行緒持有鎖
可以通過mysqladmin debug
相關等待鎖的執行緒以及誰持有鎖可以在錯誤日誌中找到
2.儲存引擎層的鎖等待則比較麻煩，以下是innodb儲存引擎中鎖等待以及哪個執行緒持有鎖的查詢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\g
3.如果因為執行緒在乙個事務中空閒而正在遭受大量的鎖操作，下面查詢顯示儲存引擎層有多少查詢被哪些執行緒阻塞。
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\g
參考資料
《高效能mysql第三版》
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