Performance Optimizations:

1. Add index on testrun.submissionId
2. replace lti_parameters.size with lti_parameters.present? to prevent COUNT query

Signed-off-by: Sebastian Serth <Sebastian.Serth@student.hpi.de>

app/helpers/lti_helper.rb

@@ -5,6 +5,6 @@ module LtiHelper
     lti_parameters = LtiParameter.where(consumers_id: consumer_id,
                                        external_users_id: external_user_id,
                                        exercises_id: exercise_id).lis_outcome_service_url?
-    !lti_parameters.nil? && lti_parameters.size > 0
+    !lti_parameters.nil? && lti_parameters.present?
   end
-end
+end