Fix N+1 problem on Api::TaxonsController#index

api/app/controllers/spree/api/taxons_controller.rb

@@ -12,7 +12,12 @@ def index
           @taxons = Spree::Taxon.accessible_by(current_ability, :read).order(:taxonomy_id, :lft).ransack(params[:q]).result
         end
 
+        unless params[:without_children]
+          @taxons = @taxons.includes(:children)
+        end
+
         @taxons = paginate(@taxons)
+        preload_taxon_parents(@taxons)
         respond_with(@taxons)
       end
 
@@ -106,6 +111,16 @@ def taxon_params
           {}
         end
       end
+
+      def preload_taxon_parents(taxons)
+        parents = Spree::Taxon.none
+
+        taxons.map do |taxon|
+          parents = parents.or(taxon.ancestors)
+        end
+
+        Spree::Taxon.associate_parents(taxons + parents)
+      end
     end
   end
 end

api/spec/requests/spree/api/taxons_controller_spec.rb

@@ -4,16 +4,14 @@
 
 module Spree
   describe Api::TaxonsController, type: :request do
-    let(:taxonomy) { create(:taxonomy) }
-    let(:taxon) { create(:taxon, name: "Ruby", taxonomy: taxonomy) }
-    let(:taxon2) { create(:taxon, name: "Rails", taxonomy: taxonomy) }
+    let!(:taxonomy) { create(:taxonomy) }
+    let!(:taxon) { create(:taxon, name: "Ruby", parent: taxonomy.root, taxonomy: taxonomy) }
+    let!(:taxon2) { create(:taxon, name: "Rails", parent: taxon, taxonomy: taxonomy) }
+    let!(:rails_v3_2_2) { create(:taxon, name: "3.2.2", parent: taxon2, taxonomy: taxonomy) }
     let(:attributes) { ["id", "name", "pretty_name", "permalink", "parent_id", "taxonomy_id"] }
 
     before do
       stub_authentication!
-      taxon2.children << create(:taxon, name: "3.2.2", taxonomy: taxonomy)
-      taxon.children << taxon2
-      taxonomy.root.children << taxon
     end
 
     context "as a normal user" do
@@ -85,6 +83,24 @@ module Spree
         end
       end
 
+      context 'filtering by taxon ids' do
+        it 'returns only requested id' do
+          get spree.api_taxons_path, params: { ids: [rails_v3_2_2.id] }
+
+          expect(json_response['taxons'].size).to eq 1
+        end
+
+        it 'returns only requested ids' do
+          # We need a completly new branch to avoid having parent that can be preloaded from the rails ancestors
+          python   = create(:taxon, name: "Python", parent: taxonomy.root, taxonomy: taxonomy)
+          python_3 = create(:taxon, name: "3.0", parent: python, taxonomy: taxonomy)
+
+          get spree.api_taxons_path, params: { ids: [rails_v3_2_2.id, python_3.id] }
+
+          expect(json_response['taxons'].size).to eq 2
+        end
+      end
+
       it "gets a single taxon" do
         get spree.api_taxonomy_taxon_path(taxonomy, taxon.id)
 

core/app/models/spree/taxon.rb

@@ -104,9 +104,14 @@ def all_variants
     # @return [String] this taxon's ancestors names followed by its own name,
     #   separated by arrows
     def pretty_name
-      ancestor_chain = ancestors.map(&:name)
-      ancestor_chain << name
-      ancestor_chain.join(" -> ")
+      if parent.present?
+        [
+          parent.pretty_name,
+          name
+        ].compact.join(" -> ")
+      else
+        name
+      end
     end
 
     # @see https://github.com/spree/spree/issues/3390