Issues with Lazy Loading and N+1 Selects in Spring Data JPA with Hibernate 5.4
I'm following best practices but I'm upgrading from an older version and I've searched everywhere and can't find a clear answer. I've searched everywhere and can't find a clear answer. I'm facing a performance issue with my Spring Data JPA application using Hibernate 5.4. I have an entity `Order` that has a `ManyToOne` relationship with an `Customer`. When I fetch a list of orders, I notice that each order triggers an additional query to load the associated customer, resulting in an N+1 selects problem. I’ve tried using `@EntityGraph` to eagerly load the customer, but it doesn’t seem to resolve the issue. Here’s the code snippet: ```java @Entity public class Order { @Id @GeneratedValue private Long id; @ManyToOne(fetch = FetchType.LAZY) private Customer customer; // other fields and methods } @EntityGraph(attributePaths = "customer") List<Order> findAll(); ``` When I run the query, I see multiple SQL queries in my logs, something like: ``` SELECT * FROM orders; SELECT * FROM customers WHERE id = ?; SELECT * FROM customers WHERE id = ?; ... ``` I also tried switching the fetch type to `EAGER` in the `Order` entity, but then I run into other issues with data duplication and performance degradation when retrieving large datasets. My repository method looks like this: ```java public interface OrderRepository extends JpaRepository<Order, Long> { @Query("SELECT o FROM Order o JOIN FETCH o.customer") List<Order> findAllWithCustomers(); } ``` However, this still does not seem to solve the N+1 issue as intended. Any suggestions on how to effectively handle this or what best practices I might be overlooking? I'd like to optimize this without compromising the lazy loading benefits for other parts of the application. My development environment is macOS. I'd really appreciate any guidance on this. I'm working in a Ubuntu 22.04 environment. I'm working in a Windows 10 environment. What's the best practice here? The stack includes Java and several other technologies.