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update sql docs
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fengzhao committed Nov 16, 2023
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2 changes: 1 addition & 1 deletion docs/basic/10.sql-Transaction.md
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Expand Up @@ -562,7 +562,7 @@ SELECT ... FOR UPDATE
在出现问题时查看 show processlist 的时候,可以看到简单的所谓的`Waiting for table metadata lock`之类的状态,有些情况很难排查。


元数据锁是server层的表级锁。主要用于隔离DML和DDL操作之间的干扰。
元数据锁是server层的表级锁。主要用于隔离DML和DDL操作之间的干扰。MDL锁不仅仅是作用在 table 上,也作用在 schemas/

每执行一条DML、DDL语句时都会申请MDL锁,DML操作需要MDL读锁,DDL操作需要MDL写锁(MDL加锁过程是系统自动控制,无法直接干预,读读共享,读写互斥,写写互斥)

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