use eager loading to reduce the number of database queries

app/controllers/execution_environments_controller.rb

@@ -34,7 +34,7 @@ class ExecutionEnvironmentsController < ApplicationController
   private :execution_environment_params
 
   def index
-    @execution_environments = ExecutionEnvironment.all.order(:name)
+    @execution_environments = ExecutionEnvironment.all.includes(:user).order(:name)
     authorize!
   end
 

app/controllers/exercises_controller.rb

@@ -78,7 +78,7 @@ class ExercisesController < ApplicationController
 
   def index
     @search = policy_scope(Exercise).search(params[:q])
-    @exercises = @search.result.order(:title)
+    @exercises = @search.result.includes(:execution_environment, :user).order(:title)
     authorize!
   end
 

app/controllers/external_users_controller.rb

@@ -5,7 +5,7 @@ class ExternalUsersController < ApplicationController
   private :authorize!
 
   def index
-    @users = ExternalUser.all
+    @users = ExternalUser.all.includes(:consumer)
     authorize!
   end
 

app/controllers/file_types_controller.rb

@@ -28,7 +28,7 @@ class FileTypesController < ApplicationController
   private :file_type_params
 
   def index
-    @file_types = FileType.all.order(:name)
+    @file_types = FileType.all.includes(:user).order(:name)
     authorize!
   end
 

app/controllers/internal_users_controller.rb

@@ -62,7 +62,7 @@ class InternalUsersController < ApplicationController
 
   def index
     @search = InternalUser.search(params[:q])
-    @users = @search.result.order(:name)
+    @users = @search.result.includes(:consumer).order(:name)
     authorize!
   end
 

app/controllers/submissions_controller.rb

@@ -34,7 +34,7 @@ class SubmissionsController < ApplicationController
 
   def index
     @search = Submission.search(params[:q])
-    @submissions = @search.result.paginate(page: params[:page])
+    @submissions = @search.result.includes(:exercise, :user).paginate(page: params[:page])
     authorize!
   end
 

app/controllers/teams_controller.rb

@@ -22,7 +22,7 @@ class TeamsController < ApplicationController
   end
 
   def index
-    @teams = Team.all.order(:name)
+    @teams = Team.all.includes(:internal_users).order(:name)
     authorize!
   end