Fix slow group loading on forking page

By preloading associations and loading membership in controller

app/controllers/projects/forks_controller.rb

@@ -43,9 +43,10 @@ class Projects::ForksController < Projects::ApplicationController
       end
 
       format.json do
-        namespaces = fork_service.valid_fork_targets - [current_user.namespace, project.namespace]
+        namespaces = load_namespaces_with_associations - [project.namespace]
+
         render json: {
-          namespaces: ForkNamespaceSerializer.new.represent(namespaces, project: project, current_user: current_user)
+          namespaces: ForkNamespaceSerializer.new.represent(namespaces, project: project, current_user: current_user, memberships: memberships_hash)
         }
       end
     end
@@ -100,6 +101,17 @@ class Projects::ForksController < Projects::ApplicationController
   def whitelist_query_limiting
     Gitlab::QueryLimiting.whitelist('https://gitlab.com/gitlab-org/gitlab-foss/issues/42335')
   end
+
+  def load_namespaces_with_associations
+    fork_service.valid_fork_targets(only_groups: true).preload(:route)
+  end
+
+  def memberships_hash
+    current_user.members.inject({}) do |memberships, member|
+      memberships[member.source_id] = member
+      memberships
+    end
+  end
 end
 
 Projects::ForksController.prepend_if_ee('EE::Projects::ForksController')

app/finders/fork_targets_finder.rb

@@ -7,8 +7,10 @@ class ForkTargetsFinder
   end
 
   # rubocop: disable CodeReuse/ActiveRecord
-  def execute
-    ::Namespace.where(id: user.manageable_namespaces).sort_by_type
+  def execute(options = {})
+    return ::Namespace.where(id: user.manageable_namespaces).sort_by_type unless options[:only_groups]
+
+    ::Group.where(id: user.manageable_namespaces)
   end
   # rubocop: enable CodeReuse/ActiveRecord
 

app/serializers/fork_namespace_entity.rb

@@ -19,7 +19,7 @@ class ForkNamespaceEntity < Grape::Entity
   end
 
   expose :permission do |namespace, options|
-    membership(options[:current_user], namespace)&.human_access
+    membership(options[:current_user], namespace, options[:memberships])&.human_access
   end
 
   expose :relative_path do |namespace|
@@ -37,10 +37,10 @@ class ForkNamespaceEntity < Grape::Entity
   private
 
   # rubocop: disable CodeReuse/ActiveRecord
-  def membership(user, object)
+  def membership(user, object, memberships)
     return unless user
 
-    @membership ||= user.members.find_by(source: object)
+    memberships[object.id]
   end
   # rubocop: enable CodeReuse/ActiveRecord
 

app/services/projects/fork_service.rb

@@ -10,8 +10,8 @@ module Projects
       forked_project
     end
 
-    def valid_fork_targets
-      @valid_fork_targets ||= ForkTargetsFinder.new(@project, current_user).execute
+    def valid_fork_targets(options = {})
+      @valid_fork_targets ||= ForkTargetsFinder.new(@project, current_user).execute(options)
     end
 
     def valid_fork_target?(namespace = target_namespace)

ee/app/controllers/ee/projects/forks_controller.rb

@@ -11,6 +11,11 @@ module EE
       def load_forks
         super.with_compliance_framework_settings
       end
+
+      override :load_namespaces_with_associations
+      def load_namespaces_with_associations
+        super.preload(:deletion_schedule)
+      end
     end
   end
 end

ee/app/finders/ee/fork_targets_finder.rb

@@ -7,7 +7,7 @@ module EE
 
     override :execute
     # rubocop: disable CodeReuse/ActiveRecord
-    def execute
+    def execute(options = {})
       targets = super
 
       root_group = project.group&.root_ancestor

spec/finders/fork_targets_finder_spec.rb

@@ -35,5 +35,13 @@ RSpec.describe ForkTargetsFinder do
     it 'returns all user manageable namespaces' do
       expect(finder.execute).to match_array([user.namespace, maintained_group, owned_group, project.namespace])
     end
+
+    it 'returns only groups when only_groups option is passed' do
+      expect(finder.execute(only_groups: true)).to match_array([maintained_group, owned_group, project.namespace])
+    end
+
+    it 'returns groups relation when only_groups option is passed' do
+      expect(finder.execute(only_groups: true)).to include(a_kind_of(Group))
+    end
   end
 end

spec/serializers/fork_namespace_entity_spec.rb

@@ -10,12 +10,19 @@ RSpec.describe ForkNamespaceEntity do
   let_it_be(:project) { create(:project) }
 
   let(:namespace) { create(:group, :with_avatar, description: 'test') }
-  let(:entity) { described_class.new(namespace, current_user: user, project: project) }
+  let(:memberships) do
+    user.members.inject({}) do |memberships, member|
+      memberships[member.source_id] = member
+      memberships
+    end
+  end
+  let(:entity) { described_class.new(namespace, current_user: user, project: project, memberships: memberships) }
 
   subject(:json) { entity.as_json }
 
   before do
     project.add_maintainer(user)
+    namespace.add_developer(user)
   end
 
   it 'renders json' do
@@ -52,7 +59,6 @@ RSpec.describe ForkNamespaceEntity do
   end
 
   it 'exposes human readable permission level' do
-    namespace.add_developer(user)
     expect(json[:permission]).to eql 'Developer'
   end