What are some examples of optimistic locking in databases?

What are some examples of optimistic locking in databases?

Optimistic locking is a concurrency control method used in databases. One common example is using a version number in a record. When a user retrieves a record, they also get its version number. When they try to update the record, the system checks if the version number matches. If it does, the update proceeds; if not, it means another transaction has modified the record.

Can you give me a specific scenario where this is applied?

Sure! Imagine a banking application where two users are trying to update the balance of the same account. User A retrieves the account balance with version 1. Meanwhile, User B also retrieves it. If User A updates the balance and submits it, the version number changes to 2. If User B tries to update the balance with version 1, the system will reject the update, preventing data inconsistency.

What happens if the update is rejected?

If the update is rejected, the application typically informs User B that their update failed due to a version conflict. User B can then refresh the data, see the latest balance, and attempt their update again with the new version number.

Are there any downsides to optimistic locking?

Yes, one downside is that it can lead to increased conflicts in high-transaction environments, which may frustrate users. Additionally, it requires careful handling of retries and user notifications.