Prevent query of calculating milestone dates when fixed dates are not used

ee/app/models/ee/epic.rb

@@ -123,12 +123,12 @@ module EE
 
     # Earliest start date from issues' milestones
     def start_date_from_milestones
-      epic_issues.joins(issue: :milestone).minimum('milestones.start_date')
+      start_date_is_fixed? ? epic_issues.joins(issue: :milestone).minimum('milestones.start_date') : start_date
     end
 
     # Latest end date from issues' milestones
     def due_date_from_milestones
-      epic_issues.joins(issue: :milestone).maximum('milestones.due_date')
+      due_date_is_fixed? ? epic_issues.joins(issue: :milestone).maximum('milestones.due_date') : due_date
     end
 
     def to_reference(from = nil, full: false)

ee/spec/models/epic_spec.rb

@@ -98,56 +98,78 @@ describe Epic do
   end
 
   describe '#start_date_from_milestones' do
-    subject { create(:epic) }
-    let(:date) { Date.new(2017, 3, 4) }
+    context 'fixed date' do
+      subject { create(:epic, :use_fixed_dates) }
+      let(:date) { Date.new(2017, 3, 4) }
 
-    before do
-      milestone1 = create(
-        :milestone,
-        start_date: date,
-        due_date: date + 10.days
-      )
-      epic_issue1 = create(:epic_issue, epic: subject)
-      epic_issue1.issue.update(milestone: milestone1)
-
-      milestone2 = create(
-        :milestone,
-        start_date: date + 5.days,
-        due_date: date + 15.days
-      )
-      epic_issue2 = create(:epic_issue, epic: subject)
-      epic_issue2.issue.update(milestone: milestone2)
+      before do
+        milestone1 = create(
+          :milestone,
+          start_date: date,
+          due_date: date + 10.days
+        )
+        epic_issue1 = create(:epic_issue, epic: subject)
+        epic_issue1.issue.update(milestone: milestone1)
+
+        milestone2 = create(
+          :milestone,
+          start_date: date + 5.days,
+          due_date: date + 15.days
+        )
+        epic_issue2 = create(:epic_issue, epic: subject)
+        epic_issue2.issue.update(milestone: milestone2)
+      end
+
+      it 'returns earliest start date from issue milestones' do
+        expect(subject.start_date_from_milestones).to eq(date)
+      end
     end
 
-    it 'returns earliest start date from issue milestones' do
-      expect(subject.start_date_from_milestones).to eq(date)
+    context 'milestone date' do
+      subject { create(:epic, start_date: date) }
+      let(:date) { Date.new(2017, 3, 4) }
+
+      it 'returns start_date' do
+        expect(subject.start_date_from_milestones).to eq(date)
+      end
     end
   end
 
   describe '#due_date_from_milestones' do
-    subject { create(:epic) }
-    let(:date) { Date.new(2017, 3, 4) }
+    context 'fixed date' do
+      subject { create(:epic, :use_fixed_dates) }
+      let(:date) { Date.new(2017, 3, 4) }
 
-    before do
-      milestone1 = create(
-        :milestone,
-        start_date: date - 30.days,
-        due_date: date - 20.days
-      )
-      epic_issue1 = create(:epic_issue, epic: subject)
-      epic_issue1.issue.update(milestone: milestone1)
-
-      milestone2 = create(
-        :milestone,
-        start_date: date - 10.days,
-        due_date: date
-      )
-      epic_issue2 = create(:epic_issue, epic: subject)
-      epic_issue2.issue.update(milestone: milestone2)
+      before do
+        milestone1 = create(
+          :milestone,
+          start_date: date - 30.days,
+          due_date: date - 20.days
+        )
+        epic_issue1 = create(:epic_issue, epic: subject)
+        epic_issue1.issue.update(milestone: milestone1)
+
+        milestone2 = create(
+          :milestone,
+          start_date: date - 10.days,
+          due_date: date
+        )
+        epic_issue2 = create(:epic_issue, epic: subject)
+        epic_issue2.issue.update(milestone: milestone2)
+      end
+
+      it 'returns latest due date from issue milestones' do
+        expect(subject.due_date_from_milestones).to eq(date)
+      end
     end
 
-    it 'returns latest due date from issue milestones' do
-      expect(subject.due_date_from_milestones).to eq(date)
+    context 'milestone date' do
+      subject { create(:epic, due_date: date) }
+      let(:date) { Date.new(2017, 3, 4) }
+
+      it 'returns due_date' do
+        expect(subject.due_date_from_milestones).to eq(date)
+      end
     end
   end