performance: Update page tree eager loading

We need to include the locker during page tree eager loading in order to
prevent N+1 queries for trees with locked pages.

Author: tvdeyen

app/controllers/alchemy/admin/pages_controller.rb

@@ -62,7 +62,8 @@ def index
         elsif @current_language.root_page
           @root_page = Alchemy::PageTreePreloader.new(
             page: @current_language.root_page,
-            user: current_alchemy_user
+            user: current_alchemy_user,
+            admin_includes: true
           ).call
         end
       end
@@ -173,7 +174,11 @@ def fold
         respond_to do |format|
           format.turbo_stream do
             if was_folded
-              @page = PageTreePreloader.new(page: @page, user: current_alchemy_user).call
+              @page = PageTreePreloader.new(
+                page: @page,
+                user: current_alchemy_user,
+                admin_includes: true
+              ).call
             else
               head 200
             end

app/services/alchemy/page_tree_preloader.rb

@@ -13,9 +13,11 @@ module Alchemy
   class PageTreePreloader
     # @param page [Page] Starting page for loading descendants
     # @param user [User, nil] User for folding support
-    def initialize(page:, user: nil)
+    # @param admin_includes [Boolean] Whether to include admin-only associations like :locker
+    def initialize(page:, user: nil, admin_includes: false)
       @page = page
       @user = user
+      @admin_includes = admin_includes
     end
 
     # Preloads and returns the page tree
@@ -43,7 +45,7 @@ def call
 
     private
 
-    attr_reader :page, :user
+    attr_reader :page, :user, :admin_includes
 
     # Load folded page IDs for the user
     def load_folded_page_ids
@@ -83,7 +85,16 @@ def preload_children_associations(pages, folded_page_ids: Set.new)
 
     # Associations to preload for sitemap rendering
     def preload_associations
-      [:public_version, {language: {site: :languages}}]
+      associations = [
+        {
+          language: {
+            site: :languages
+          }
+        },
+        :public_version
+      ]
+      associations.push(:locker) if admin_includes
+      associations
     end
   end
 

spec/services/alchemy/page_tree_preloader_spec.rb

@@ -39,6 +39,10 @@
       expect(subject.language.association(:site)).to be_loaded
     end
 
+    it "does not preload locker association" do
+      expect(subject.association(:locker)).not_to be_loaded
+    end
+
     context "with folded pages" do
       before do
         child_page_1.fold!(user.id, true)
@@ -60,5 +64,19 @@
         expect(subject.children.first.children).to eq([grandchild_page])
       end
     end
+
+    context "with admin_includes: true" do
+      subject do
+        described_class.new(
+          page: root_page.reload,
+          user: user,
+          admin_includes: true
+        ).call
+      end
+
+      it "preloads locker association" do
+        expect(subject.association(:locker)).to be_loaded
+      end
+    end
   end
 end