Optimize Empty Submission Querying in graders_controller

Changelog.md

@@ -12,6 +12,7 @@
 - Ensures row selection for peer reviewer unassigning has the same validation checks as individual selections (#7274)
 - Ensures mark levels on a rubric criterion are properly scaled when its max mark is updated (#7311)
 - Refactor contributors list in About section to read from markus-contributors.txt (#7374)
+- Optimized the querying of submissions when assigning graders (#7381)
 
 ### 🔧 Internal changes
 

app/controllers/graders_controller.rb

@@ -253,10 +253,8 @@ def unassign_graders(grouping_ids, grader_ids)
 
   # Returns array of grouping ids with non empty submissions
   def filter_empty_submissions(grouping_ids)
-    grouping_ids.select do |grouping_id|
-      submission = Submission.find_by(grouping_id: grouping_id, submission_version_used: true)
-      submission && !submission.is_empty
-    end
+    Submission.where(grouping_id: grouping_ids, is_empty: false, submission_version_used: true)
+              .pluck(:grouping_id)
   end
 
   def filter_grouping_by_section(section_assignments, assignment)

spec/controllers/graders_controller_spec.rb

@@ -761,6 +761,28 @@
               expect(@grouping1.tas).to be_empty
             end
           end
+
+          context 'when empty submissions are filtered' do
+            let(:submission) { create(:version_used_submission, grouping: @grouping1, is_empty: false) }
+            let(:submission2) { create(:version_used_submission, grouping: @grouping2, is_empty: true) }
+            # purposefully not creating submission3
+
+            it 'filters out grouping2 and grouping3' do
+              groupings = [@grouping1, @grouping2, @grouping3]
+              post_as @instructor, :global_actions, params: {
+                course_id: course.id,
+                assignment_id: @assignment.id,
+                global_actions: 'assign',
+                groupings: groupings,
+                graders: [@ta1.id],
+                current_table: 'groups_table',
+                skip_empty_submissions: 'true'
+              }
+
+              filtered_grouping_ids = GradersController.new.__send__(:filter_empty_submissions, groupings)
+              expect(filtered_grouping_ids).to contain_exactly(@grouping1.id)
+            end
+          end
         end
       end