Resolve remaining N+1 in Search API (Advanced) projects scope

app/models/namespace.rb

@@ -287,6 +287,8 @@ class Namespace < ApplicationRecord
   end
 
   def root_ancestor
+    return self if persisted? && parent_id.nil?
+
     strong_memoize(:root_ancestor) do
       self_and_ancestors.reorder(nil).find_by(parent_id: nil)
     end

app/models/project.rb

@@ -524,7 +524,7 @@ class Project < ApplicationRecord
 
   scope :with_api_entity_associations, -> {
     preload(:project_feature, :route, :tags,
-            group: :ip_restrictions, namespace: [:route, :owner])
+            group: [:ip_restrictions, :saml_provider], namespace: [:route, :owner])
   }
 
   scope :with_api_commit_entity_associations, -> {

changelogs/unreleased/218703-fix-api-projects-search-n-plus-1.yml

+---
+title: Resolve N+1 in Search API projects scope
+merge_request: 35833
+author:
+type: performance

ee/spec/lib/gitlab/auth/group_saml/gma_membership_enforcer_spec.rb

@@ -5,10 +5,10 @@ require 'spec_helper'
 RSpec.describe Gitlab::Auth::GroupSaml::GmaMembershipEnforcer do
   include ProjectForksHelper
 
-  let_it_be(:group) { create(:group_with_managed_accounts, :private) }
-  let_it_be(:project) { create(:project, namespace: group)}
-  let_it_be(:managed_user) { create(:user, :group_managed, managing_group: group) }
-  let_it_be(:managed_user_for_project) { create(:user, :group_managed, managing_group: group) }
+  let(:group) { create(:group_with_managed_accounts, :private) }
+  let(:project) { create(:project, namespace: group)}
+  let(:managed_user) { create(:user, :group_managed, managing_group: group) }
+  let(:managed_user_for_project) { create(:user, :group_managed, managing_group: group) }
 
   subject { described_class.new(project) }
 

spec/models/namespace_spec.rb

@@ -884,8 +884,13 @@ RSpec.describe Namespace do
   end
 
   describe '#root_ancestor' do
+    let!(:root_group) { create(:group) }
+
+    it 'returns root_ancestor for root group without a query' do
+      expect { root_group.root_ancestor }.not_to exceed_query_limit(0)
+    end
+
     it 'returns the top most ancestor' do
-      root_group = create(:group)
       nested_group = create(:group, parent: root_group)
       deep_nested_group = create(:group, parent: nested_group)
       very_deep_nested_group = create(:group, parent: deep_nested_group)