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Ultimate Guide to N+1 Loading Problem in Hibernate/JPA
When working with Hibernate or Java Persistence API (JPA), you may sometimes come across a performance issue known as the N+1 loading problem. It’s a common problem that can slow down your application, but don’t worry! In this guide, we’ll learn what this problem is, why it happens, and how we can fix it. Let’s dive in with easy-to-understand words and helpful examples.
Understanding the N+1 Loading Problem
Imagine you are at a supermarket with a list of items to buy. You pick a cart, and for each item on your list, you go to its aisle, pick it, and come back to the checkout counter before going for the next item. After picking all items, you finally purchase everything at once. This process is inefficient because you are making too many trips. A better way is to collect all the items in your cart first and then make a single trip to the counter to pay.
This is similar to what happens in the N+1 loading problem. When you ask Hibernate or JPA to fetch a list of things from the database, like grabbing all your groceries, instead of getting them in one go, it might make one request for the list and then an additional request for each item to get more details. If you have 10 items, then that’s 1 (for the list) + 10 (detailed queries) = 11 trips to the database, thus the name N+1.