From b195a4ce34e3787bca3a14aa59131b7e9586a24c Mon Sep 17 00:00:00 2001
From: Philipp Thun <philipp.thun@sap.com>
Date: Wed, 6 Jul 2022 11:15:22 +0200
Subject: [PATCH] Improve query to check if broker has service instances

Instead of doing (more than) m times n queries (number of services *
number of service plans) a single query joining the required tables is
sufficient.

before
------
1*    SELECT * FROM `services` WHERE (`service_broker_id` = ...)
m*    SELECT * FROM `service_plans` WHERE (`service_id` = ...)
m*n*  SELECT * FROM `service_instances` WHERE (`service_plan_id` = ...)

after
-----
SELECT 1 AS `one`
  FROM `service_instances`
  INNER JOIN `service_plans`
    ON (`service_plans`.`id` = `service_instances`.`service_plan_id`)
  INNER JOIN `services`
    ON (`services`.`id` = `service_plans`.`service_id`)
  WHERE (`services`.`service_broker_id` = 1)
  LIMIT 1
---
 app/models/services/service_broker.rb         | 10 ++++----
 .../models/services/service_broker_spec.rb    | 25 +++++++++++++++----
 2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/app/models/services/service_broker.rb b/app/models/services/service_broker.rb
index 536507f4576..b8fd08314f5 100644
--- a/app/models/services/service_broker.rb
+++ b/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)
diff --git a/spec/unit/models/services/service_broker_spec.rb b/spec/unit/models/services/service_broker_spec.rb
index 0c151a4d8be..62808fbcbb6 100644
--- a/spec/unit/models/services/service_broker_spec.rb
+++ b/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