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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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