Bulk update epics when milestone date changes

ee/app/models/ee/epic.rb

@@ -170,8 +170,6 @@ module EE
       super.merge(label_url_method: :group_epics_url)
     end
 
-    private
-
     def fetch_milestone_date_data
       sql = <<~SQL
         SELECT milestones.id, milestones.start_date, milestones.due_date FROM milestones

ee/app/services/ee/milestones/update_service.rb

@@ -9,12 +9,42 @@ module EE
       def execute(milestone)
         super
 
-        ::Epic.joins(:issues).where(issues: { milestone_id: milestone.id }).each do |epic|
-          epic.update_dates
+        if milestone.previous_changes.key?(:start_date) || milestone.previous_changes.key?(:due_date)
+          update_epics(milestone)
         end
 
         milestone
       end
+
+      private
+
+      def update_epics(milestone)
+        groups = ::Epic.joins(:issues).includes(:issues).where(issues: { milestone_id: milestone.id }).group_by do |epic|
+          milestone_ids = epic.issues.map(&:milestone_id)
+          milestone_ids.compact!
+          milestone_ids.uniq!
+          milestone_ids
+        end
+
+        groups.each do |milestone_ids, epics|
+          data = epics.first.fetch_milestone_date_data
+
+          ::Epic.where(id: epics.map(&:id)).update_all(
+            [
+              %{
+                start_date = CASE WHEN start_date_is_fixed = true THEN start_date ELSE ? END,
+                start_date_sourcing_milestone_id = ?,
+                end_date = CASE WHEN due_date_is_fixed = true THEN end_date ELSE ? END,
+                due_date_sourcing_milestone_id = ?
+              },
+              data[:start_date],
+              data[:start_date_sourcing_milestone_id],
+              data[:due_date],
+              data[:due_date_sourcing_milestone_id]
+            ]
+          )
+        end
+      end
     end
   end
 end

ee/spec/services/milestones/update_service_spec.rb

@@ -17,7 +17,10 @@ describe Milestones::UpdateService do
 
         epic.reload
 
+        expect(epic.start_date).to eq(nil)
+        expect(epic.start_date_sourcing_milestone).to eq(nil)
         expect(epic.due_date).to eq(due_date)
+        expect(epic.due_date_sourcing_milestone).to eq(milestone)
       end
     end
   end