Improve query to check if broker has service instances

app/models/services/service_broker.rb

@@ -47,11 +47,11 @@ def space_scoped?
     end
 
     def has_service_instances?
-      services.select do |service|
-        service.service_plans.select { |plan|
-          plan.service_instances.any?
-        }.any?
-      end.any?
+      !VCAP::CloudController::ServiceInstance.
+        join(:service_plans, id: :service_plan_id).
+        join(:services, id: :service_id).
+        where(services__service_broker_id: id).
+        empty?
     end
 
     def self.user_visibility_filter(user)

spec/unit/models/services/service_broker_spec.rb

@@ -203,13 +203,28 @@ module VCAP::CloudController
       let(:service) { Service.make(service_broker: service_broker) }
       let!(:service_plan) { ServicePlan.make(service: service) }
 
-      it 'returns true when there are service instances' do
-        ManagedServiceInstance.make(service_plan: service_plan)
-        expect(service_broker.has_service_instances?).to eq(true)
+      context 'when there are service instances' do
+        before do
+          ManagedServiceInstance.make(service_plan: service_plan)
+        end
+
+        it 'returns true' do
+          expect(service_broker.has_service_instances?).to eq(true)
+        end
+
+        it 'does a single db query' do
+          expect { service_broker.has_service_instances? }.to have_queried_db_times(/select/i, 1)
+        end
       end
 
-      it 'return false when there are no service instances' do
-        expect(service_broker.has_service_instances?).to eq(false)
+      context 'when there are no service instances' do
+        it 'returns false' do
+          expect(service_broker.has_service_instances?).to eq(false)
+        end
+
+        it 'does a single db query' do
+          expect { service_broker.has_service_instances? }.to have_queried_db_times(/select/i, 1)
+        end
       end
     end
   end