Fix & Refactor BackendAPI scopes: orphans & not_used_by

  - Use not_exists instead of not_in for the possible null values.
  - Do it through BabySqueel and unscoping the order in the subquery to make it work in
Oracle.
  - Test .orphans with disable_transactional_fixtures! to not have null
values like in the real execution.

app/models/backend_api.rb

@@ -37,25 +37,20 @@ class BackendApi < ApplicationRecord
 
   has_system_name(uniqueness_scope: [:account_id])
 
-  scope :orphans, -> { where.has { id.not_in(BackendApiConfig.selecting { :backend_api_id }) } }
+  scope :orphans, -> {
+    where.has do
+      not_exists(BackendApiConfig.except(:order).by_backend_api(BabySqueel[:backend_apis].id).select(:id))
+    end
+  }
 
   scope :not_used_by, ->(service_id) {
-    # TODO: Baby Squeel
-    # It should be:
-    # where.has do
-    #   not_exists BackendApiConfig.by_service(service_id).by_backend_api(BabySqueel[:backend_apis].id).select(:id)
-    # end
-    # And that works for MySQL and Postgres but not Oracle
-    sql_query = <<~SQL
-      (
-        NOT EXISTS (
-          SELECT id
-          FROM backend_api_configs
-          WHERE service_id = ? AND backend_api_configs.backend_api_id = backend_apis.id
-        )
+    where.has do
+      not_exists(
+        BackendApiConfig.except(:order).select(:id)
+          .by_service(service_id)
+          .by_backend_api(BabySqueel[:backend_apis].id)
       )
-    SQL
-    where(sql_query, service_id)
+    end
   }
 
   scope :oldest_first, -> { order(created_at: :asc) }

lib/tasks/backend_api.rake

@@ -3,6 +3,9 @@
 namespace :backend_api do
   desc 'Destroy all orphan backend apis that does not belongs to any service when api_as_product is disabled'
   task :destroy_orphans => :environment do
-    BackendApi.orphans.find_each { |backend_api| DeleteObjectHierarchyWorker.perform_later(backend_api) unless backend_api.account.provider_can_use?(:api_as_product) }
+    BackendApi.orphans.joins(:account).select(:id, :account_id).find_each do |backend_api|
+      next if backend_api.account.provider_can_use?(:api_as_product)
+      DeleteObjectHierarchyWorker.perform_later(backend_api)
+    end
   end
 end

test/models/backend_api_test.rb

@@ -31,19 +31,6 @@ def test_default_api_backend
     assert @backend_api.valid?
   end
 
-  test '.orphans should return backend apis that do not belongs to any service' do
-    account = FactoryBot.create(:account)
-    FactoryBot.create(:service, account: account)
-    service_to_delete = FactoryBot.create(:simple_service, :with_default_backend_api, system_name: 'orphan_system', account: account)
-    orphan_backend_api = service_to_delete.backend_api_configs.first.backend_api
-
-    assert_equal [], BackendApi.orphans
-
-    service_to_delete.destroy!
-
-    assert_equal [orphan_backend_api], BackendApi.orphans
-  end
-
   test '.not_used_by returns the backend apis that are not related to that service' do
     account = FactoryBot.create(:simple_provider)
     backend_api_not_used_by_any_service = FactoryBot.create(:backend_api, account: account)
@@ -93,7 +80,7 @@ def test_default_api_backend
     refute BackendApi.exists? backend_api.id
   end
 
-  class ProxyConfigAffectingChangesTest < ActiveSupport::TestCase
+  class DisableTransactionalFixturesTest < ActiveSupport::TestCase
     disable_transactional_fixtures!
 
     test 'proxy config affecting changes on update' do
@@ -108,5 +95,20 @@ class ProxyConfigAffectingChangesTest < ActiveSupport::TestCase
       backend_api.update_attributes(private_endpoint: 'http://new-endpoint')
       backend_api.update_attributes(name: 'New Backend Name')
     end
+
+    test '.orphans should return backend apis that do not belongs to any service' do
+      account = FactoryBot.create(:account)
+      FactoryBot.create(:service, account: account)
+      service_to_delete = FactoryBot.create(:simple_service, :with_default_backend_api, system_name: 'orphan_system', account: account)
+      orphan_backend_api = service_to_delete.backend_api_configs.first.backend_api
+
+      assert_equal [], BackendApi.orphans.pluck(:id)
+
+      service_to_delete.destroy!
+      assert_equal 0, orphan_backend_api.services.count
+      assert_equal 0, orphan_backend_api.backend_api_configs.count
+
+      assert_equal [orphan_backend_api.id], BackendApi.orphans.pluck(:id)
+    end
   end
 end