#196250 adding preload to prevent N+1

app/controllers/profiles/notifications_controller.rb

@@ -4,13 +4,14 @@ class Profiles::NotificationsController < Profiles::ApplicationController
   # rubocop: disable CodeReuse/ActiveRecord
   def show
     @user = current_user
-    @group_notifications = current_user.notification_settings.for_groups.order(:id)
+    @group_notifications = current_user.notification_settings.preload_source_route.for_groups.order(:id)
     @group_notifications += GroupsFinder.new(
       current_user,
       all_available: false,
       exclude_group_ids: @group_notifications.select(:source_id)
     ).execute.map { |group| current_user.notification_settings_for(group, inherit: true) }
     @project_notifications = current_user.notification_settings.for_projects.order(:id)
+                             .preload_source_route
                              .select { |notification| current_user.can?(:read_project, notification.source) }
     @global_notification_setting = current_user.global_notification_setting
   end

app/models/notification_setting.rb

@@ -27,6 +27,8 @@ class NotificationSetting < ApplicationRecord
       .where.not(projects: { pending_delete: true })
   end
 
+  scope :preload_source_route, -> { preload(source: [:route]) }
+
   EMAIL_EVENTS = [
     :new_release,
     :new_note,

changelogs/unreleased/196250.yml

+---
+title: Remove N+1 query for profile notifications
+merge_request: 22845
+author: Ohad Dahan
+type: performance

spec/controllers/profiles/notifications_controller_spec.rb

@@ -24,7 +24,6 @@ describe Profiles::NotificationsController do
     context 'with groups that do not have notification preferences' do
       set(:group) { create(:group) }
       set(:subgroup) { create(:group, parent: group) }
-
       before do
         group.add_developer(user)
       end

spec/requests/profiles/notifications_controller_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'view user notifications' do
+  let(:user) do
+    create(:user) do |user|
+      user.emails.create(email: 'original@example.com')
+      user.emails.create(email: 'new@example.com')
+      user.notification_email = 'original@example.com'
+      user.save!
+    end
+  end
+
+  before do
+    login_as(user)
+
+    create_list(:group, 2) do |group|
+      group.add_developer(user)
+    end
+  end
+
+  def get_profile_notifications
+    get profile_notifications_path
+  end
+
+  describe 'GET /profile/notifications' do
+    it 'avoid N+1 due to an additional groups (with no parent group)' do
+      get_profile_notifications
+
+      control = ActiveRecord::QueryRecorder.new do
+        get_profile_notifications
+      end
+
+      create_list(:group, 2) { |group| group.add_developer(user) }
+
+      expect do
+        get_profile_notifications
+      end.not_to exceed_query_limit(control)
+    end
+  end
+end