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2025-04-04 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Database >
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Create table if not exists Waiting for table metadata lock
Version mysql 5.5
Phenomenon:
Mysql > show full processlist
+-+-+ -+
| | Id | User | Host | db | Command | Time | State | Info |
+-+-+ -+
| | 1 | event_scheduler | localhost | NULL | Daemon | 1661254 | Waiting on empty queue | NULL | |
| | 4 | root | localhost | test | Query | 13 | Waiting for table metadata lock | create table if not exists a like t | |
| | 5 | root | localhost | test | Sleep | 32 | | NULL |
| | 7 | root | localhost | NULL | Query | 0 | NULL | show full processlist | |
+-+-+ -+
Mysql > select * from information_schema.innodb_trx\ G
Empty set (0.00 sec)
No lock found.
Reproduce:
Session 1:
Create table a (id int) engine=myisam
Begin
Select * from a
Session2:
Create table if not exists a like t
.... Wait.
Session 3:
Mysql > show full processlist
+-+-+ -+
| | Id | User | Host | db | Command | Time | State | Info |
+-+-+ -+
| | 1 | event_scheduler | localhost | NULL | Daemon | 1661796 | Waiting on empty queue | NULL | |
| | 5 | root | localhost | test | Sleep | 51 | | NULL |
| | 7 | root | localhost | NULL | Query | 0 | NULL | show full processlist | |
| | 10 | root | localhost | test | Query | 40 | Waiting for table metadata lock | create table if not exists a like t | |
+-+-+ -+
4 rows in set (0.00 sec)
Mysql > select * from information_schema.innodb_trx\ G
Empty set (0.00 sec)
If table an is defined as innodb, the record can be queried through select * from information_schema.innodb_trx\ G
In addition:
Version 5.6 does not have this problem.
Please indicate the source of the reprint.
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