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This article mainly introduces the relevant knowledge of "what is the concept of mysql metadata lock". The editor shows you the operation process through an actual case, and the operation method is simple, fast and practical. I hope this article "what is the concept of MySQL metadata lock" can help you solve the problem.

1. MDL does not need to be used explicitly and will be added automatically when it is accessed.

2. The function of MDL is to ensure the correctness of reading and writing.

You can imagine that if a query is traversing the data in a table and another thread changes the structure of the table and deletes a column during execution, the results obtained by the query thread must not match the structure of the table.

3. MDL is introduced in the MySQL5.5 version, adding a MDL read lock when adding, deleting, modifying and querying a table.

When making structural changes to the table, add a MDL write lock.

Example

This is the end of the introduction of the content of "what is the concept of MySQL metadata lock" in session Avatar begin select * from stu;#commin; / / session B:alter table stu add T1 int; / / session C:show processlist;. Thank you for your reading. If you want to know more about the industry, you can follow the industry information channel. The editor will update different knowledge points for you every day.

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