MySQL Stored Procedure Programming

Name

SQL-04: Use an appropriate locking strategy

Synopsis

There are two major patterns in transaction management: the optimistic locking strategy and the pessimistic locking strategy.

The pessimistic locking strategy assumes that concurrent updates are quite likely. To prevent this, the transaction locks rows as they are read. Other transactions that want to update the row must wait until the pessimistic transaction ends.

The optimistic locking strategy assumes that in the period of time between a user reading and then updating a row, it is unlikely that another user will attempt to update that same row. Of course, optimism in and of itself is not sufficient; when following this locking strategy, the program should check to ensure that the row has not been updated, immediately prior to the update. If the row has been updated, then the transaction is aborted.

Each locking strategy is based on assumptions regarding the behavior of other transactions or application users. Each has different implications for the duration of any locks acquired during the transaction and the possibility that a transaction will be aborted. Make sure that you weigh carefully the implications of the two strategies and pick the approach that best suits your application.