2 files changed, 154 insertions, 0 deletions
diff --git a/spec/models/preloaders/project_policy_preloader_spec.rb b/spec/models/preloaders/project_policy_preloader_spec.rb
new file mode 100644
index 00000000000..79f232f5ce2
--- /dev/null
+++ b/spec/models/preloaders/project_policy_preloader_spec.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Preloaders::ProjectPolicyPreloader do
+  let_it_be(:user) { create(:user) }
+  let_it_be(:root_parent) { create(:group, :private, name: 'root-1', path: 'root-1') }
+  let_it_be(:guest_project) { create(:project, name: 'public guest', path: 'public-guest') }
+  let_it_be(:private_maintainer_project) do
+    create(:project, :private, name: 'b private maintainer', path: 'b-private-maintainer', namespace: root_parent)
+  end
+
+  let_it_be(:private_developer_project) do
+    create(:project, :private, name: 'c public developer', path: 'c-public-developer')
+  end
+
+  let_it_be(:public_maintainer_project) do
+    create(:project, :private, name: 'a public maintainer', path: 'a-public-maintainer')
+  end
+
+  let(:base_projects) do
+    Project.where(id: [guest_project, private_maintainer_project, private_developer_project, public_maintainer_project])
+  end
+
+  before_all do
+    guest_project.add_guest(user)
+    private_maintainer_project.add_maintainer(user)
+    private_developer_project.add_developer(user)
+    public_maintainer_project.add_maintainer(user)
+  end
+
+  it 'avoids N+1 queries when authorizing a list of projects', :request_store do
+    preload_projects_for_policy(user)
+    control = ActiveRecord::QueryRecorder.new { authorize_all_projects(user) }
+
+    new_project1 = create(:project, :private).tap { |project| project.add_maintainer(user) }
+    new_project2 = create(:project, :private, namespace: root_parent)
+
+    another_root = create(:group, :private, name: 'root-3', path: 'root-3')
+    new_project3 = create(:project, :private, namespace: another_root).tap { |project| project.add_maintainer(user) }
+
+    pristine_projects = Project.where(id: base_projects + [new_project1, new_project2, new_project3])
+
+    preload_projects_for_policy(user, pristine_projects)
+    expect { authorize_all_projects(user, pristine_projects) }.not_to exceed_query_limit(control)
+  end
+
+  def authorize_all_projects(current_user, project_list = base_projects)
+    project_list.each { |project| current_user.can?(:read_project, project) }
+  end
+
+  def preload_projects_for_policy(current_user, project_list = base_projects)
+    described_class.new(project_list, current_user).execute
+  end
+end
diff --git a/spec/models/preloaders/project_root_ancestor_preloader_spec.rb b/spec/models/preloaders/project_root_ancestor_preloader_spec.rb
new file mode 100644
index 00000000000..30036a6a033
--- /dev/null
+++ b/spec/models/preloaders/project_root_ancestor_preloader_spec.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Preloaders::ProjectRootAncestorPreloader do
+  let_it_be(:root_parent1) { create(:group, :private, name: 'root-1', path: 'root-1') }
+  let_it_be(:root_parent2) { create(:group, :private, name: 'root-2', path: 'root-2') }
+  let_it_be(:guest_project) { create(:project, name: 'public guest', path: 'public-guest') }
+  let_it_be(:private_maintainer_project) do
+    create(:project, :private, name: 'b private maintainer', path: 'b-private-maintainer', namespace: root_parent1)
+  end
+
+  let_it_be(:private_developer_project) do
+    create(:project, :private, name: 'c public developer', path: 'c-public-developer')
+  end
+
+  let_it_be(:public_maintainer_project) do
+    create(:project, :private, name: 'a public maintainer', path: 'a-public-maintainer', namespace: root_parent2)
+  end
+
+  let(:root_query_regex) { /\ASELECT.+FROM "namespaces" WHERE "namespaces"."id" = \d+/ }
+  let(:additional_preloads) { [] }
+  let(:projects) { [guest_project, private_maintainer_project, private_developer_project, public_maintainer_project] }
+  let(:pristine_projects) { Project.where(id: projects) }
+
+  shared_examples 'executes N matching DB queries' do |expected_query_count, query_method = nil|
+    it 'executes the specified root_ancestor queries' do
+      expect do
+        pristine_projects.each do |project|
+          root_ancestor = project.root_ancestor
+
+          root_ancestor.public_send(query_method) if query_method.present?
+        end
+      end.to make_queries_matching(root_query_regex, expected_query_count)
+    end
+
+    it 'strong_memoizes the correct root_ancestor' do
+      pristine_projects.each do |project|
+        expected_parent_id = project.root_ancestor&.id
+
+        expect(project.parent_id).to eq(expected_parent_id)
+      end
+    end
+  end
+
+  context 'when use_traversal_ids FF is enabled' do
+    context 'when the preloader is used' do
+      before do
+        preload_ancestors
+      end
+
+      context 'when no additional preloads are provided' do
+        it_behaves_like 'executes N matching DB queries', 0
+      end
+
+      context 'when additional preloads are provided' do
+        let(:additional_preloads) { [:route] }
+        let(:root_query_regex) { /\ASELECT.+FROM "routes" WHERE "routes"."source_id" = \d+/ }
+
+        it_behaves_like 'executes N matching DB queries', 0, :full_path
+      end
+    end
+
+    context 'when the preloader is not used' do
+      it_behaves_like 'executes N matching DB queries', 4
+    end
+  end
+
+  context 'when use_traversal_ids FF is disabled' do
+    before do
+      stub_feature_flags(use_traversal_ids: false)
+    end
+
+    context 'when the preloader is used' do
+      before do
+        preload_ancestors
+      end
+
+      context 'when no additional preloads are provided' do
+        it_behaves_like 'executes N matching DB queries', 4
+      end
+
+      context 'when additional preloads are provided' do
+        let(:additional_preloads) { [:route] }
+        let(:root_query_regex) { /\ASELECT.+FROM "routes" WHERE "routes"."source_id" = \d+/ }
+
+        it_behaves_like 'executes N matching DB queries', 4, :full_path
+      end
+    end
+
+    context 'when the preloader is not used' do
+      it_behaves_like 'executes N matching DB queries', 4
+    end
+  end
+
+  def preload_ancestors
+    described_class.new(pristine_projects, :namespace, additional_preloads).execute
+  end
+end