How to prevent N+1 query issues when using nested associations with Rails ActiveRecord?
I'm getting frustrated with Hey everyone, I'm running into an issue that's driving me crazy... I'm working on a project and hit a roadblock. I'm working on a personal project and I'm working with serious performance optimization in my Rails application due to N+1 query problems when fetching nested associations. Using Rails 6.1 with Postgres, I have the following models: ```ruby class User < ApplicationRecord has_many :posts end class Post < ApplicationRecord belongs_to :user has_many :comments end class Comment < ApplicationRecord belongs_to :post end ``` When I try to display a list of users along with their posts and comments, I use this code: ```ruby @users = User.all @users.each do |user| user.posts.each do |post| post.comments.each do |comment| puts "User: #{user.name}, Post: #{post.title}, Comment: #{comment.body}" end end end ``` This results in a important number of queries being executed (one for each user, one for each post, and one for each comment), leading to performance degradation. I tried using `includes` to eager load the associations like this: ```ruby @users = User.includes(posts: :comments).all ``` However, I still notice that the number of queries executed isn't significantly reduced, and the output is not as expected. I get an `ActiveRecord::StatementInvalid` behavior intermittently while loading the comments, suggesting that the eager loading isn't set up correctly. I also tried using `joins`, but it does not work well with the nested structure I have. Can someone guide me on how to properly set up eager loading for nested associations in this case to eliminate the N+1 scenario? Any insights on best practices for this scenario would be greatly appreciated! What am I doing wrong? I'm working on a application that needs to handle this. Has anyone dealt with something similar?