Recently tried to re-depth study MVCC principle, the following collection of good articles for later reference
MVCC principle explore and implement MySQL source code analysis
InnoDB MVCC implementation principle and source parsing
MySQL InnoDB multi-version concurrency control (MVCC)
Read the above article was found, MVCC mechanism is there is a problem, is defective.
Question: In the RR case, the transaction A transaction modifies data after opening a, but did not submit commit; this time after the transaction B is on matters to do multiple queries data a; if transaction A complete submission commit, or multiple transaction B data queries data a, the first time a query data query. That is, the use of old data.
In the RC case, not the problem.
Cause: RR level, the first time the snapshot was created when read read view, under the RC level, read each snapshot will create a new read view
