Refactor UsersController to not kill the database

Previously this controller would in multiple places load tons (read:
around 65000) project and/or group IDs into memory. These changes in
combination with the previous commits significantly cut down loading
times of user profile pages and the Atom feeds of users.

app/controllers/users_controller.rb

@@ -3,14 +3,11 @@ class UsersController < ApplicationController
   before_action :set_user
 
   def show
-    @contributed_projects = contributed_projects.joined(@user).
-      reject(&:forked?)
+    @contributed_projects = contributed_projects.joined(@user).reject(&:forked?)
 
-    @projects = @user.personal_projects.
-      where(id: authorized_projects_ids).includes(:namespace)
+    @projects = PersonalProjectsFinder.new(@user).execute(current_user)
 
-    # Collect only groups common for both users
-    @groups = @user.groups & GroupsFinder.new.execute(current_user)
+    @groups = JoinedGroupsFinder.new(@user).execute(current_user)
 
     respond_to do |format|
       format.html
@@ -53,16 +50,8 @@ class UsersController < ApplicationController
     @user = User.find_by_username!(params[:username])
   end
 
-  def authorized_projects_ids
-    # Projects user can view
-    @authorized_projects_ids ||=
-      ProjectsFinder.new.execute(current_user).pluck(:id)
-  end
-
   def contributed_projects
-    @contributed_projects = Project.
-      where(id: authorized_projects_ids & @user.contributed_projects_ids).
-      includes(:namespace)
+    ContributedProjectsFinder.new(@user).execute(current_user)
   end
 
   def contributions_calendar
@@ -73,9 +62,13 @@ class UsersController < ApplicationController
   def load_events
     # Get user activity feed for projects common for both users
     @events = @user.recent_events.
-      where(project_id: authorized_projects_ids).
-      with_associations
+      merge(projects_for_current_user).
+      references(:project).
+      with_associations.
+      limit_recent(20, params[:offset])
+  end
 
-    @events = @events.limit(20).offset(params[:offset] || 0)
+  def projects_for_current_user
+    ProjectsFinder.new.execute(current_user)
   end
 end

spec/controllers/users_controller_spec.rb

@@ -16,15 +16,28 @@ describe UsersController do
     context 'with rendered views' do
       render_views
 
-      it 'renders the show template' do
+      describe 'when logged in' do
+        before do
           sign_in(user)
+        end
 
+        it 'renders the show template' do
           get :show, username: user.username
 
           expect(response).to be_success
           expect(response).to render_template('show')
         end
       end
+
+      describe 'when logged out' do
+        it 'renders the show template' do
+          get :show, username: user.username
+
+          expect(response).to be_success
+          expect(response).to render_template('show')
+        end
+      end
+    end
   end
 
   describe 'GET #calendar' do