How does CascadeType.LOCK works in JPA and Hibernate

Introduction Having introduced Hibernate explicit locking support, as well as Cascade Types, it’s time to analyze the CascadeType.LOCK behavior. A Hibernate lock request triggers an internal LockEvent. The associated DefaultLockEventListener may cascade the lock request to the locking entity children. Since CascadeType.ALL includes CascadeType.LOCK too, it’s worth understanding when a lock request propagates from a Parent to a Child entity.

How do LockModeType.PESSIMISTIC_READ and LockModeType.PESSIMISTIC_WRITE work in JPA and Hibernate

Introduction Java Persistence API comes with a thorough concurrency control mechanism, supporting both implicit and explicit locking. The implicit locking mechanism is straightforward and it relies on: Optimistic locking: Entity state changes can trigger a version incrementation Row-level locking: Based on the current running transaction isolation level, the INSERT/UPDATE/DELETE statements may acquire exclusive row locks While implicit locking is suitable for many scenarios, an explicit locking mechanism can leverage a finer-grained concurrency control. In my previous posts, I covered the explicit optimistic lock modes: OPTIMISTIC OPTIMISTIC_FORCE_INCREMENT PESSIMISTIC_FORCE_INCREMENT In this post, I am… Read More

How does LockModeType.PESSIMISTIC_FORCE_INCREMENT work in JPA and Hibernate

Introduction In my previous post, I introduced the OPTIMISTIC_FORCE_INCREMENT Lock Mode and we applied it for propagating a child entity version change to a locked parent entity. In this post, I am going to reveal the PESSIMISTIC_FORCE_INCREMENT Lock Mode and compare it with its optimistic counterpart.

How does LockModeType.OPTIMISTIC_FORCE_INCREMENT work in JPA and Hibernate

Introduction In my previous post, I explained how OPTIMISTIC Lock Mode works and how it can help us synchronize external entity state changes. In this post, we are going to unravel the OPTIMISTIC_FORCE_INCREMENT Lock Mode usage patterns. With LockModeType.OPTIMISTIC, the locked entity version is checked towards the end of the current running transaction, to make sure we don’t use a stale entity state. Because of the application-level validation nature, this strategy is susceptible to race-conditions, therefore requiring an additional pessimistic lock . The LockModeType.OPTIMISTIC_FORCE_INCREMENT not only it checks the expected locked entity… Read More

How to fix optimistic locking race conditions with pessimistic locking

Recap In my previous post, I explained the benefits of using explicit optimistic locking. As we then discovered, there’s a very short time window in which a concurrent transaction can still commit a Product price change right before our current transaction gets committed. This issue can be depicted as follows: Alice fetches a Product She then decides to order it The Product optimistic lock is acquired The Order is inserted in the current transaction database session The Product version is checked by the Hibernate explicit optimistic locking routine The price engine manages… Read More

How does LockModeType.OPTIMISTIC work in JPA and Hibernate

Explicit optimistic locking In my previous post, I introduced the basic concepts of Java Persistence locking. The implicit locking mechanism prevents lost updates and it’s suitable for entities that we can actively modify. While implicit optimistic locking is a widespread technique, few happen to understand the inner workings of explicit optimistic lock mode. Explicit optimistic locking may prevent data integrity anomalies when the locked entities are always modified by some external mechanism.

Logical vs physical clock optimistic locking

Introduction In my previous post I demonstrated why optimistic locking is the only viable solution for application-level transactions. Optimistic locking requires a version column that can be represented as: a physical clock (a timestamp value taken from the system clock) a logical clock (an incrementing numeric value) This article will demonstrate why logical clocks are better suited for optimistic locking mechanisms. System time The system time is provided by the operating system internal clocking algorithm. The programmable interval timer periodically sends an interrupt signal (with a frequency of 1.193182 MHz). The CPU… Read More