Fix epics search query

Fix epics search query when CTE is enabled

ee/app/finders/epics_finder.rb

@@ -55,7 +55,6 @@ class EpicsFinder < IssuableFinder
     items = init_collection
     items = by_created_at(items)
     items = by_updated_at(items)
-    items = by_search(items)
     items = by_author(items)
     items = by_timeframe(items)
     items = by_state(items)
@@ -64,6 +63,12 @@ class EpicsFinder < IssuableFinder
     items = by_iids(items)
     items = starts_with_iid(items)
 
+    # This has to be last as we use a CTE as an optimization fence
+    # for counts by passing the force_cte param and enabling the
+    # attempt_group_search_optimizations feature flag
+    # https://www.postgresql.org/docs/current/static/queries-with.html
+    items = by_search(items)
+
     sort(items)
   end
 

ee/spec/finders/epics_finder_spec.rb

@@ -272,6 +272,21 @@ describe EpicsFinder do
             expect { epics(iid_starts_with: '-1') }.to raise_error(ArgumentError)
           end
         end
+
+        context 'when using group cte for search' do
+          context 'and two labels more search string are present' do
+            let_it_be(:label1) { create(:label) }
+            let_it_be(:label2) { create(:label) }
+            let!(:labeled_epic) { create(:labeled_epic, group: group, title: 'filtered epic', labels: [label1, label2]) }
+
+            it 'returns correct epics' do
+              filtered_epics =
+                epics(attempt_group_search_optimizations: true, label_name: [label1.title, label2.title], search: 'filtered')
+
+              expect(filtered_epics).to contain_exactly(labeled_epic)
+            end
+          end
+        end
       end
     end
   end