MVCC multi-version concurrency control

What is a MVCC

MVCC implements transaction read and write concurrency (implements read and write concurrency)

Realization principle of MVCC

MVCC is implemented through the version chain. The update operation in THE MVCC generates a new version snapshot in the version chain. The snapshot is stored in the undo log, and the undo log connects all the snapshots through the roll_ptr pointer to form the version chain. MVCC query operation adopts snapshot read, without locking, along the version chain read to meet the conditions of the data; The update operation of MVCC uses the current read, which reads the latest version of data and needs to be locked.