optimizations when doing pluck / calculations

spec/loading_optimizations_spec.rb

@@ -15,41 +15,129 @@ RSpec.describe "loading optimizations" do
       )
     end
 
-    it "queries only the aux table if no main table columns are referenced" do
-      queries =
-        SpecHelper.capture_queries do
-          expect(Car.pluck(:fuel_type)).to eq(%w[gasoline hybrid electric])
-        end
-
-      expect(queries.length).to eq(1)
-      expect(queries.first).not_to include("JOIN")
+    shared_examples "queries only the aux table" do
+      it "queries only the aux table" do
+        expect(@queries.length).to eq(1)
+        expect(@queries.first).not_to include("JOIN")
+        expect(@queries.first).to match(/\bvehicles_car_aux\b/)
+        expect(@queries.first).not_to match(/\bvehicles\b/)
+      end
     end
 
-    it "queries only the aux table if all columns are on the aux table" do
-      queries =
-        SpecHelper.capture_queries do
-          expect(Car.where(engine_size: 1.4..1.9).pluck(:fuel_type)).to eq(
-            %w[hybrid electric]
-          )
-        end
-
-      expect(queries.length).to eq(1)
-      expect(queries.first).not_to include("JOIN")
-      expect(queries.first).to include("BETWEEN")
-      expect(queries.first).to match(/\bvehicles_car_aux\b/)
-      expect(queries.first).not_to match(/\bvehicles\b/)
+    shared_examples "queries both tables" do
+      it "queries both tables" do
+        expect(@queries.length).to eq(1)
+        expect(@queries.first).to include("JOIN")
+        expect(@queries.first).to match(/\bvehicles\b/)
+        expect(@queries.first).to match(/\bvehicles_car_aux\b/)
+      end
     end
 
-    it "queries both tables if main table column is referenced" do
-      queries =
-        SpecHelper.capture_queries do
-          rel = Car.where(name: "Toyota Camry")
-          rel = rel.pluck(:fuel_type)
-          expect(rel).to eq(%w[gasoline])
+    describe "pluck" do
+      context "aux columns are referenced" do
+        before do
+          @queries =
+            SpecHelper.capture_queries do
+              expect(Car.pluck(:fuel_type)).to eq(%w[gasoline hybrid electric])
+            end
         end
 
-      expect(queries.length).to eq(1)
-      expect(queries.first).to include("JOIN")
+        it_behaves_like "queries only the aux table"
+      end
+
+      context "aux columns are chained on a where clause" do
+        before do
+          @queries =
+            SpecHelper.capture_queries do
+              expect(Car.where(engine_size: 1.4..1.9).pluck(:fuel_type)).to eq(
+                %w[hybrid electric]
+              )
+            end
+        end
+
+        it_behaves_like "queries only the aux table"
+        it "applies the BETWEEN clause" do
+          expect(@queries.first).to include("BETWEEN")
+        end
+      end
+
+      context "main table columns are referenced" do
+        before do
+          @queries =
+            SpecHelper.capture_queries do
+              expect(Car.where(name: "Toyota Camry").pluck(:fuel_type)).to eq(
+                %w[gasoline]
+              )
+            end
+        end
+
+        it_behaves_like "queries both tables"
+      end
+
+      context "main table columns are chained on a where clause" do
+        before do
+          @queries =
+            SpecHelper.capture_queries do
+              expect(Car.where(name: "Toyota Camry").pluck(:fuel_type)).to eq(
+                %w[gasoline]
+              )
+            end
+        end
+
+        it_behaves_like "queries both tables"
+      end
+    end
+
+    describe "maximum" do
+      context "aux columns are referenced" do
+        before do
+          @queries =
+            SpecHelper.capture_queries do
+              expect(Car.maximum(:engine_size)).to eq(2.0)
+            end
+        end
+
+        it_behaves_like "queries only the aux table"
+      end
+
+      context "aux columns are chained on a where clause" do
+        before do
+          @queries =
+            SpecHelper.capture_queries do
+              expect(
+                Car.where(engine_size: 1.4..1.9).maximum(:engine_size)
+              ).to eq(1.8)
+            end
+        end
+
+        it_behaves_like "queries only the aux table"
+      end
+
+      context "main table columns are referenced" do
+        before do
+          @queries =
+            SpecHelper.capture_queries do
+              expect(
+                Car.where(name: "Toyota Camry").maximum(:engine_size)
+              ).to eq(2.0)
+            end
+        end
+
+        it_behaves_like "queries both tables"
+      end
+
+      context "main table columns are chained on a where clause" do
+        before do
+          @queries =
+            SpecHelper.capture_queries do
+              expect(
+                Car.where(name: "Toyota Camry").maximum(:engine_size)
+              ).to eq(2.0)
+            end
+        end
+
+        it_behaves_like "queries both tables"
+      end
     end
   end
 end