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n_plus_one_query_optimization

🚀 Optimize N+1 Queries with Eager Loading​

By default, ActiveRecord can issue one query per associated record, leading to N+1 issues. In controllers, preload associations to avoid excessive database hits. Use includes or eager_load when fetching collections, especially for JSON APIs or index pages.

class PostsController < ApplicationController
  def index
    # Preloads comments and author in a single query
    @posts = Post.includes(:comments, :author).order(created_at: :desc)
    render json: @posts.to_json(include: [:comments, :author])
  end
end

You can also scope your eager loading to specific attributes:

@posts = Post.includes(comments: [:user]).select(:id, :title, :created_at)