What are the advantages and disadvantages of using optimistic and pessimistic locking in database testing?

1 What is optimistic locking?

Optimistic locking is a strategy that assumes that data conflicts are rare and allows transactions to access and modify data without acquiring locks. Instead, it checks for conflicts at the end of the transaction, before committing the changes to the database. If a conflict is detected, the transaction is aborted and restarted, or the user is notified to resolve the conflict manually. Optimistic locking is suitable for database systems that have low contention and high concurrency, where locking would cause too much overhead and delay.

2 What is pessimistic locking?

Pessimistic locking is a strategy that assumes that data conflicts are common and prevents transactions from accessing and modifying data that is already locked by another transaction. It acquires locks on the data as soon as the transaction starts, and releases them when the transaction ends. Pessimistic locking ensures that data is consistent and isolated, but it also reduces concurrency and performance, as transactions have to wait for locks to be released or may cause deadlocks.

3 Advantages of optimistic locking

Optimistic locking offers several advantages for database testing, such as improved performance and scalability due to fewer locks being acquired and released, thus reducing network and database overhead. Additionally, it enhances concurrency and availability as transactions do not block each other, allowing them to access and modify data simultaneously, thus increasing the throughput and responsiveness of the database system. Finally, optimistic locking avoids deadlocks as transactions do not hold locks for a long time and do not depend on other transactions to release locks.

5 Advantages of pessimistic locking

Pessimistic locking offers several advantages for database testing, such as ensuring data consistency and integrity. Transactions lock the data they access and modify, preventing other transactions from interfering or reading uncommitted data. This simplifies the transaction logic and management, as transactions don't have to check for conflicts or handle rollback or resolution. Additionally, pessimistic locking reduces the number of aborts and retries, as transactions are less likely to encounter conflicts or fail to commit. This improves the stability and predictability of the test outcome.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?