Optimize SQL to replace N+1 in Groups:Analytics#show

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/models/push_event_payload.rb

@@ -22,3 +22,5 @@ class PushEventPayload < ActiveRecord::Base
     tag: 1
   }
 end
+
+PushEventPayload.prepend(EE::PushEventPayload)

ee/app/models/ee/push_event_payload.rb

+# frozen_string_literal: true
+
+module EE
+  module PushEventPayload
+    extend ActiveSupport::Concern
+
+    class_methods do
+      def commit_count_for(events)
+        where(event_id: events).sum(:commit_count)
+      end
+    end
+  end
+end

ee/app/views/groups/analytics/show.html.haml

@@ -22,7 +22,7 @@
 
   %h3 Push
   - code_push_count = @events.code_push.count
-  - commits_count = @events.code_push.map(&:commits_count).sum # rubocop: disable CodeReuse/ActiveRecord
+  - commits_count = PushEventPayload.commit_count_for(@events.code_push)
   - person_count = @events.code_push.pluck(:author_id).uniq.count # rubocop: disable CodeReuse/ActiveRecord
   - person_count_string = pluralize person_count, 'person'
   - pushes_string = _('<strong>%{pushes}</strong> pushes, more than <strong>%{commits}</strong> commits by <strong>%{people}</strong> contributors.').html_safe % { pushes: code_push_count, commits: commits_count , people: person_count_string }

ee/changelogs/unreleased/index-for-groups-analytic-controller-4899.yml

+---
+title: Solve a N+1 issue in Groups::AnalyticsController
+merge_request: 4508
+author:
+type: performance

ee/spec/controllers/groups/analytics_controller_spec.rb

@@ -111,14 +111,13 @@ describe Groups::AnalyticsController do
     render_views
 
     it 'avoids a N+1 query in #show' do
-      control_count = ActiveRecord::QueryRecorder.new { get :show, params: { group_id: group.path } }.count
+      # Warm the cache
+      get :show, params: { group_id: group.path }
 
-      # Clear out controller state to force a refresh of the group
-      controller.instance_variable_set(:@group, nil)
-      user4 = create(:user)
-      group.add_user(user4, GroupMember::DEVELOPER)
+      control_queries = ActiveRecord::QueryRecorder.new { get :show, params: { group_id: group.path } }
+      create_push_event(user, project)
 
-      expect { get :show, params: { group_id: group.path } }.not_to exceed_query_limit(control_count)
+      expect { get :show, params: { group_id: group.path } }.not_to exceed_query_limit(control_queries)
     end
   end