Fix another repeating queries

app/services/labels/find_or_create_service.rb

@@ -6,7 +6,7 @@ module Labels
       @current_user = current_user
       @parent = parent
       @available_labels = params.delete(:available_labels)
-      @existing_labels_by_title = params.delete(:existing_labels_by_title) || {}
+      @existing_labels_by_title = params.delete(:existing_labels_by_title)
       @params = params.dup.with_indifferent_access
     end
 
@@ -45,7 +45,9 @@ module Labels
 
     # rubocop: disable CodeReuse/ActiveRecord
     def find_existing_label(title)
-      existing_labels_by_title[title] || available_labels.find_by(title: title)
+      return existing_labels_by_title[title] if existing_labels_by_title
+
+      available_labels.find_by(title: title)
     end
     # rubocop: enable CodeReuse/ActiveRecord
 

changelogs/unreleased/194104-part-2.yml

+---
+title: Fix repeating SQL queries when changing labels for a resource.
+merge_request: 60718
+author:
+type: performance

ee/lib/api/epics.rb

@@ -115,8 +115,6 @@ module API
         at_least_one_of :title, :description, :start_date_fixed, :start_date_is_fixed, :due_date_fixed, :due_date_is_fixed, :labels, :add_labels, :remove_labels, :state_event, :confidential
       end
       put ':id/(-/)epics/:epic_iid' do
-        Gitlab::QueryLimiting.disable!('https://gitlab.com/gitlab-org/gitlab/issues/194104')
-
         authorize_can_admin_epic!
 
         # Setting updated_at is allowed only for admins and owners

spec/services/labels/find_or_create_service_spec.rb

@@ -25,6 +25,35 @@ RSpec.describe Labels::FindOrCreateService do
           project.add_developer(user)
         end
 
+        context 'when existing_labels_by_title is provided' do
+          let(:preloaded_label) { build(:label, title: 'Security') }
+
+          before do
+            params.merge!(
+              existing_labels_by_title: {
+                'Security' => preloaded_label
+              })
+          end
+
+          context 'when label exists' do
+            it 'returns preloaded label' do
+              expect(service.execute).to eq preloaded_label
+            end
+          end
+
+          context 'when label does not exists' do
+            before do
+              params[:title] = 'Audit'
+            end
+
+            it 'does not generates additional label search' do
+              service.execute
+
+              expect(LabelsFinder).not_to receive(:new)
+            end
+          end
+        end
+
         context 'when label does not exist at group level' do
           it 'creates a new label at project level' do
             expect { service.execute }.to change(project.labels, :count).by(1)