MySQL optimistic lock

Optimistic locking holds that concurrent operations on the same data will not always occur , It's a small probability event , You don't have to lock the data every time , But in the process of updating, we will judge whether other people have updated this data during this period , That is to say Do not use the locking mechanism of the database itself , But through Program to achieve . On procedure , We can use Version number mechanism perhaps CAS Mechanism Realization . Optimistic lock is suitable for multi read applications , This can improve throughput . stay Java in java.util.concurrent.atomic The atomic variable class under the package is an implementation method that uses optimistic locking ：CAS Realized .
1. Optimistic lock version number mechanism ： Design a... In the table Version field version , The first time I read it , Will get version Value of field . Then update or delete the data , Will execute UPDATE ... SET version=version+1 WHERE version=version . At this time, if a transaction has changed this data , The modification will not succeed .
2. The timestamp mechanism of optimistic lock ： Timestamp is the same as the version number mechanism , It's also when the update is submitted , Compare the timestamp of the current data with that obtained before the update , If both are consistent, the update is successful , Otherwise it's a version conflict . As you can see, optimistic lock is the programmer's permission to control the concurrent operation of data , Basically by adding a stamp to the data row （ Version number or time stamp ）, So as to prove whether the current data is up-to-date .