Locking Mechanisms
Understand how database locks maintain integrity through different strategies, granularities, and modes.
We'll cover the following...
Imagine our online store is having a massive flash sale.
Two customers, Alice and Bob, are trying to buy the very last "Laptop" in stock. They both add it to their cart and click “Buy Now” at the exact same moment. What should happen? If the system isn’t careful, it might process both orders, check the stock (which is 1), and sell the same laptop twice.
This would lead to one very unhappy customer and a logistical nightmare for the store.
This is a classic concurrency problem, where multiple actions happening at the same time can corrupt our data. To prevent this chaos, databases use a powerful tool: locking mechanisms. In this lesson, we’ll explore how databases manage simultaneous access to data, ensuring everything stays consistent and accurate.
By the end of this lesson, we will be able to:
Understand why locking is essential for maintaining data integrity in a multi-user environment.
Differentiate between the two main locking strategies: pessimistic and optimistic locking.
Explain the concept of lock granularity, including row-level and table-level locks.
Describe the difference between shared and exclusive lock modes.
Let’s dive in and see how we can keep our data safe and sound.
Need for locking
Locking is the mechanism that enforces the “I” in ACID: Isolation. Isolation ensures that even when multiple transactions run concurrently, they don’t interfere with one another.
It creates the illusion that each transaction executes independently, as if they were processed sequentially. Without proper management, concurrency can cause serious issues, such as the flash sale problem, where one user’s transaction affects another’s, resulting in inconsistent or incorrect data. ...