mysql - MySQL Multiple table locks

Question

I have a small curiosity about MySQL table locks.

Say I want to lock two tables. I execute this command:

LOCK TABLES table1 WRITE, table2 WRITE

And then I checked if the tables have indeed been locked by executing:

SHOW OPEN TABLES IN mydatabase WHERE In_use > 0

I have noticed tho that if I run two lock commands sequentitally for example:

LOCK TABLES table1 WRITE
LOCK TABLES table2 WRITE

And then check which tables are locked using the same command only table2 is marked as locked. Why is this so?

Thanks

Answer 1

LOCK TABLES不是事务安全的，它会在尝试锁定表之前隐式提交任何活动事务。

所以，在第一种情况下，你有一个事务持有 2 个表被锁定，在第二个只有一个，因为LOCK TABLES table1 WRITE已经提交

Answer 2

锁定表会先解锁当前会话锁定的所有表，然后再执行指定的锁定。所以锁定表 2 的调用是解锁表 1。