Talk about mvcc multi version concurrency controller?

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MVCC What is it? ？

MVCC It is a multi version concurrent controller , It is generally used for concurrent access to databases .MVCC Do not use locks to control transactions , And it can solve dirty reading 、 Non repeatability 、 Fantasy reading .（ Unable to solve the problem of missing updates .）

Specific operation

Innodb Each row of data has an upward pointing version data stored in undo log in , Form a version chain .
If the record is updated , The latest data will be written to undo log in , And the hidden pointer points to the previous version .
At this point, the query will find the last undo log edition .
MVCC benefits ： Read without lock 、 Read write conflict , Increased concurrency , Guaranteed business .

Please correct me if there is any mistake