| Comments

Rails Fix N+1 Query

How to fix N+1 query in Rails ?

I try to explain fix N+1 on example. Let’s start, firstly, in your rails application, you created association between user and user_profile models like below :

1
2
3

class User < ActiveRecord::Base
   has_one :profile, class_name: 'UserProfile'
end

and

1
2
3

class UserProfile < ActiveRecord::Base
  belongs_to :user
end

When you created association between user and user_profile like above (you can derive it), then you are getting like below error while you refresh to app page or edit something… The error is that :

1
2
3
4
5
6

The page at 0.0.0.0:3000 says:
user:-----
N+1 Query detected
User => [:profile]
Add to your finder::include => [:profile]
N+1 Query method call stack

Actually rails says to you for fix above bug(it says use include to profile…), for fix bug open users_controller.rb then add :

1

User.includes(:profile)

instead of

1

User

like below ;

1
2
3
4
5
6

class UsersController < ApplicationController
    def index
        @search = User.includes(:profile).search(params[:q])
        @users = @search.result(:distinct => true).paginate(:page => params[:page])
    end
end

That’s it.

I hope helped to you .

Comments