MVCC of Google's Fragmented Notes (Draft)

MVCC multi-version concurrency control

(The first understanding is not necessarily correct, let’s continue later)
The implementation of MVCC in MySQL InnoDB is mainly to improve the concurrent performance of the database, to deal with read-write conflicts in a better way, so that even if there are read and writeIn the event of conflict, it can also achieve non-locking, non-blocking concurrent reading
ReadView is the basis for extracting data from MVCC during snapshot execution;
1, snapshot read: select query statement;
2, current read: query before data operation at update, insert, delete;

ReadView is a data structure

The value is to compare the data with TRX_ID