Use linear version GroupsWithTemplatesFinder#extended_group_search

Changelog: performance
EE: true

config/feature_flags/development/linear_groups_template_finder_extended_group_search.yml

+---
+name: linear_groups_template_finder_extended_group_search
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68936
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/339439
+milestone: '14.3'
+type: development
+group: group::access
+default_enabled: false

ee/app/finders/groups_with_templates_finder.rb

@@ -24,7 +24,12 @@ class GroupsWithTemplatesFinder
       .base_and_ancestors
       .with_feature_available_in_plan(:group_project_templates)
 
-    Gitlab::ObjectHierarchy.new(groups_with_plan).base_and_descendants
+    # We're adding an extra query that will be removed once we remove the feature flag in https://gitlab.com/gitlab-org/gitlab/-/issues/339439
+    if ::Feature.enabled?(:linear_groups_template_finder_extended_group_search, current_group, default_enabled: :yaml)
+      groups_with_plan.self_and_descendants
+    else
+      Gitlab::ObjectHierarchy.new(groups_with_plan).base_and_descendants
+    end
   end
 
   def simple_group_search(groups)
@@ -33,4 +38,9 @@ class GroupsWithTemplatesFinder
 
     groups.with_project_templates
   end
+
+  # This method will be removed https://gitlab.com/gitlab-org/gitlab/-/issues/339439
+  def current_group
+    Group.find_by(id: group_id) # rubocop:disable CodeReuse/ActiveRecord
+  end
 end

ee/spec/finders/groups_with_templates_finder_spec.rb

@@ -26,56 +26,37 @@ RSpec.describe GroupsWithTemplatesFinder do
     create(:gitlab_subscription, :premium, namespace: group_2)
   end
 
-  describe 'without group id' do
-    it 'returns all groups' do
-      expect(described_class.new.execute).to contain_exactly(group_1, group_2, group_3)
-    end
-
-    context 'when namespace checked' do
-      before do
-        allow(Gitlab::CurrentSettings).to receive(:should_check_namespace_plan?) { true }
-      end
-
-      it 'returns groups on ultimate/premium plan' do
-        expect(described_class.new.execute).to contain_exactly(group_1, group_2)
+  shared_examples 'group template finder examples' do
+    describe 'without group id' do
+      it 'returns all groups' do
+        expect(described_class.new.execute).to contain_exactly(group_1, group_2, group_3)
       end
 
-      context 'with subgroup with template' do
+      context 'when namespace checked' do
         before do
-          subgroup_4.update!(custom_project_templates_group_id: subgroup_5.id)
-          create(:project, namespace: subgroup_5)
+          allow(Gitlab::CurrentSettings).to receive(:should_check_namespace_plan?) { true }
         end
 
         it 'returns groups on ultimate/premium plan' do
-          expect(described_class.new.execute).to contain_exactly(group_1, group_2, subgroup_4)
+          expect(described_class.new.execute).to contain_exactly(group_1, group_2)
         end
-      end
-    end
-  end
-
-  describe 'with group id' do
-    it 'returns given group with it descendants' do
-      expect(described_class.new(group_1.id).execute).to contain_exactly(group_1)
-    end
 
-    context 'with subgroup with template' do
-      before do
-        subgroup_4.update!(custom_project_templates_group_id: subgroup_5.id)
-        create(:project, namespace: subgroup_5)
-      end
+        context 'with subgroup with template' do
+          before do
+            subgroup_4.update!(custom_project_templates_group_id: subgroup_5.id)
+            create(:project, namespace: subgroup_5)
+          end
 
-      it 'returns only chosen group' do
-        expect(described_class.new(group_1.id).execute).to contain_exactly(group_1)
+          it 'returns groups on ultimate/premium plan' do
+            expect(described_class.new.execute).to contain_exactly(group_1, group_2, subgroup_4)
+          end
+        end
       end
     end
 
-    context 'when namespace checked' do
-      before do
-        allow(Gitlab::CurrentSettings).to receive(:should_check_namespace_plan?) { true }
-      end
-
-      it 'does not return the group' do
-        expect(described_class.new(group_3.id).execute).to be_empty
+    describe 'with group id' do
+      it 'returns given group with it descendants' do
+        expect(described_class.new(group_1.id).execute).to contain_exactly(group_1)
       end
 
       context 'with subgroup with template' do
@@ -87,11 +68,42 @@ RSpec.describe GroupsWithTemplatesFinder do
         it 'returns only chosen group' do
           expect(described_class.new(group_1.id).execute).to contain_exactly(group_1)
         end
+      end
+
+      context 'when namespace checked' do
+        before do
+          allow(Gitlab::CurrentSettings).to receive(:should_check_namespace_plan?) { true }
+        end
 
-        it 'returns only chosen subgroup' do
-          expect(described_class.new(subgroup_4.id).execute).to contain_exactly(group_1, subgroup_4)
+        it 'does not return the group' do
+          expect(described_class.new(group_3.id).execute).to be_empty
+        end
+
+        context 'with subgroup with template' do
+          before do
+            subgroup_4.update!(custom_project_templates_group_id: subgroup_5.id)
+            create(:project, namespace: subgroup_5)
+          end
+
+          it 'returns only chosen group' do
+            expect(described_class.new(group_1.id).execute).to contain_exactly(group_1)
+          end
+
+          it 'returns only chosen subgroup' do
+            expect(described_class.new(subgroup_4.id).execute).to contain_exactly(group_1, subgroup_4)
+          end
         end
       end
     end
   end
+
+  it_behaves_like 'group template finder examples'
+
+  context 'when feature flag :linear_groups_template_finder_extended_group_search is disabled' do
+    before do
+      stub_feature_flags(linear_groups_template_finder_extended_group_search: false)
+    end
+
+    it_behaves_like 'group template finder examples'
+  end
 end