Optimize empty submission querying in GradesController#filter_empty_s…

…ubmissions (#7381)

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

@@ -561,6 +561,7 @@
           @grouping1 = create(:grouping, assignment: @assignment)
           @grouping2 = create(:grouping, assignment: @assignment)
           @grouping3 = create(:grouping, assignment: @assignment)
+          @grouping4 = create(:grouping, assignment: @assignment)
           @ta1 = create(:ta)
           @ta2 = create(:ta)
           @ta3 = create(:ta)
@@ -762,6 +763,38 @@
             end
           end
         end
+
+        context 'and when assigning to multiple groupings and skip_empty_submissions is true' do
+          before do
+            # defining submissions for use in the 'asisgn' post
+            submission
+            submission2
+            submission3
+            submission4
+            post_as @instructor,
+                    :global_actions,
+                    params: { course_id: course.id, assignment_id: @assignment.id, global_actions: 'assign',
+                              groupings: [@grouping1.id, @grouping2.id, @grouping3.id, @grouping4.id],
+                              graders: [@ta1.id], current_table: 'groups_table', skip_empty_submissions: 'true' }
+          end
+
+          context 'and some groups have empty submissions while some do not' do
+            let(:submission) { create(:version_used_submission, grouping: @grouping1, is_empty: true) }
+            let(:submission2) { create(:version_used_submission, grouping: @grouping2, is_empty: false) }
+            let(:submission3) { create(:version_used_submission, grouping: @grouping3, is_empty: true) }
+            let(:submission4) { create(:version_used_submission, grouping: @grouping4, is_empty: false) }
+
+            it 'should not assign graders to groups with empty submissions' do
+              expect(@grouping1.tas).to be_empty
+              expect(@grouping3.tas).to be_empty
+            end
+
+            it 'should assign graders to groups with non-empty submissions' do
+              expect(@grouping2.tas).to include(@ta1)
+              expect(@grouping4.tas).to include(@ta1)
+            end
+          end
+        end
       end
 
       context 'POST on :global_actions on assign_sections' do