Mysql 锁原理很多和Oracle 相似

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TRANSACTIONS
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Trx id counter 62657
Purge done for trx's n:o < 62653 undo n:o < 0 state: running but idle
History list length 142
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 24480, OS thread handle 0x7f9468122700, query id 166496 localhost root init
show engine innodb status
---TRANSACTION 62656, not started
MySQL thread id 22213, OS thread handle 0x7f94681a4700, query id 166492 localhost root cleaning up
---TRANSACTION 0, not started
MySQL thread id 10738, OS thread handle 0x7f94800a2700, query id 74172 localhost rooot cleaning up
---TRANSACTION 62655, ACTIVE 236 sec
1 lock struct(s), heap size 360, 0 row lock(s), undo log entries 1
MySQL thread id 24478, OS thread handle 0x7f9468163700, query id 166491 localhost rooot cleaning up
Trx read view will not see trx with id >= 62656, sees < 62656



------------
TRANSACTIONS
------------
Trx id counter 62657
Purge done for trx's n:o < 62653 undo n:o < 0 state: running but idle
History list length 142
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 24480, OS thread handle 0x7f9468122700, query id 166498 localhost root init
show engine innodb status
---TRANSACTION 62656, not started
MySQL thread id 22213, OS thread handle 0x7f94681a4700, query id 166497 localhost root Waiting for table metadata lock
drop table t1
--堵塞的回话执行的sql 是drop table t1
---TRANSACTION 0, not started
MySQL thread id 10738, OS thread handle 0x7f94800a2700, query id 74172 localhost rooot cleaning up
---TRANSACTION 62655, ACTIVE 288 sec
1 lock struct(s), heap size 360, 0 row lock(s), undo log entries 1
MySQL thread id 24478, OS thread handle 0x7f9468163700, query id 166491 localhost rooot cleaning up
Trx read view will not see trx with id >= 62656, sees < 62656