Merge branch '276944-reduce-lcp-to-2-5s-for-sourcecode_mr_list' into 'master'

Fix N+1 Issue with loading approval rules

See merge request gitlab-org/gitlab!52364

ee/app/controllers/concerns/ee/issuable_collections.rb

@@ -9,7 +9,7 @@ module EE
     def preload_for_collection
       @preload_for_collection ||= case collection_type
                                   when 'MergeRequest'
-                                    super.push(:approval_rules)
+                                    super + [approval_rules: [:users, :group_users], approval_project_rules: [:users, :group_users]]
                                   when 'Issue'
                                     super.push(*issue_preloads)
                                   else

ee/changelogs/unreleased/276944-reduce-lcp-to-2-5s-for-sourcecode_mr_list.yml

+---
+title: Resolve N+1 issue loading approval rules on the MR list
+merge_request: 52364
+author:
+type: performance

ee/spec/controllers/projects/merge_requests_controller_spec.rb

@@ -60,39 +60,6 @@ RSpec.describe Projects::MergeRequestsController do
     sign_in(viewer)
   end
 
-  describe 'GET index' do
-    def get_merge_requests
-      get :index,
-        params: {
-          namespace_id: project.namespace.to_param,
-          project_id: project,
-          state: 'opened'
-        }
-    end
-
-    context 'when filtering by opened state' do
-      context 'with opened merge requests' do
-        render_views
-        it 'avoids N+1' do
-          other_user = create(:user)
-          create(:merge_request, :unique_branches, target_project: project, source_project: project)
-          create_list(:approval_merge_request_rule, 5, merge_request: merge_request, users: [user, other_user], approvals_required: 2)
-
-          control_count = ActiveRecord::QueryRecorder.new { get_merge_requests }.count
-
-          create_list(:approval, 10)
-          create_list(:merge_request, 20, :unique_branches, target_project: project, source_project: project).each do |mr|
-            create(:approval_merge_request_rule, merge_request: merge_request, users: [user, other_user], approvals_required: 2)
-          end
-
-          expect do
-            get_merge_requests
-          end.not_to exceed_query_limit(control_count)
-        end
-      end
-    end
-  end
-
   describe 'PUT update' do
     let_it_be_with_reload(:merge_request) do
       create(:merge_request_with_diffs, source_project: project, author: author)

ee/spec/requests/projects/merge_requests_controller_spec.rb

@@ -43,4 +43,27 @@ RSpec.describe Projects::MergeRequestsController do
       end
     end
   end
+
+  describe 'GET #index' do
+    def get_index
+      get project_merge_requests_path(project, state: 'opened')
+    end
+
+    it 'avoids N+1' do
+      other_user = create(:user)
+      create(:merge_request, :unique_branches, target_project: project, source_project: project)
+      create_list(:approval_project_rule, 5, project: project, users: [user, other_user], approvals_required: 2)
+      create_list(:approval_merge_request_rule, 5, merge_request: merge_request, users: [user, other_user], approvals_required: 2)
+
+      control_count = ActiveRecord::QueryRecorder.new { get_index }.count
+
+      create_list(:approval, 10)
+      create(:approval_project_rule, project: project, users: [user, other_user], approvals_required: 2)
+      create_list(:merge_request, 20, :unique_branches, target_project: project, source_project: project).each do |mr|
+        create(:approval_merge_request_rule, merge_request: mr, users: [user, other_user], approvals_required: 2)
+      end
+
+      expect { get_index }.not_to exceed_query_limit(control_count)
+    end
+  end
 end