Imagine an auction system. Ten users bid on the same item. With @Version , nine users will get OptimisticLockException . You retry. The database churns. Performance collapses.
// Fast: Fetches only what you need, immutable, no persistence context overhead List<PostDTO> posts = entityManager.createQuery("select new com.dto.PostDTO(p.id, p.title) from Post p", PostDTO.class).getResultList(); Why is this faster than the book's PDF suggests? Because you remove the Entity Manager from the equation. No snapshots. No comparisons. Just data transfer. Vlad Mihalcea’s book is fantastic, but the concepts evolve faster than print. If you search for a static PDF, you freeze your knowledge in time. high-performance java persistence book pdf
But high-performance persistence isn't about avoiding JPA; it is about understanding the database driver . Imagine an auction system
The high-performance secret? Instead of updating item.current_price , you append a bid to a separate bid_history table and calculate the price on the fly via a materialized view. You bypass the lock entirely. You retry