Revert "Fix possible doubling of contact objects after race"

app/controllers/epp/domains_controller.rb

@@ -103,19 +103,13 @@ module Epp
     def update
       authorize! :update, @domain, @password
 
-      updated = Domain.transaction(isolation: isolation_level) do
-        @domain.update(params[:parsed_frame], current_user)
-      end
+      updated = @domain.update(params[:parsed_frame], current_user)
       (handle_errors(@domain) && return) unless updated
 
       pending = @domain.epp_pending_update.present?
       render_epp_response "/epp/domains/success#{'_pending' if pending}"
     end
 
-    def isolation_level
-      :serializable unless Rails.env.test?
-    end
-
     def delete
       authorize! :delete, @domain, @password
 

db/migrate/20200622080240_add_unique_constraints_to_domain_objects.rb

@@ -1,25 +0,0 @@
-class AddUniqueConstraintsToDomainObjects < ActiveRecord::Migration[6.0]
-  def up
-    execute <<-SQL
-      alter table domain_contacts
-        add constraint uniq_contact_of_type_per_domain unique (domain_id, type, contact_id);
-    SQL
-
-    execute <<-SQL
-      alter table nameservers
-        add constraint uniq_hostname_per_domain unique (domain_id, hostname);
-    SQL
-  end
-
-  def down
-    execute <<-SQL
-      alter table domain_contacts
-        drop constraint if exists uniq_contact_of_type_per_domain;
-    SQL
-
-    execute <<-SQL
-      alter table nameservers
-        drop constraint if exists uniq_hostname_per_domain;
-    SQL
-  end
-end

test/models/contact_test.rb

@@ -177,7 +177,7 @@ class ContactTest < ActiveSupport::TestCase
 
   def test_linked_when_in_use_as_domain_contact
     Domain.update_all(registrant_id: contacts(:william).id)
-    DomainContact.first.update(contact_id: @contact.id)
+    DomainContact.update_all(contact_id: @contact.id)
 
     assert @contact.linked?
   end

test/models/domain_test.rb

@@ -137,9 +137,9 @@ class DomainTest < ActiveSupport::TestCase
     contact = contacts(:john)
 
     domain.admin_contacts << contact
-    assert_raise ActiveRecord::RecordNotUnique do
-      domain.admin_contacts << contact
-    end
+    domain.admin_contacts << contact
+
+    assert domain.invalid?
   end
 
   def test_invalid_when_the_same_tech_contact_is_linked_twice
@@ -147,9 +147,9 @@ class DomainTest < ActiveSupport::TestCase
     contact = contacts(:john)
 
     domain.tech_contacts << contact
-    assert_raise ActiveRecord::RecordNotUnique do
-      domain.tech_contacts << contact
-    end
+    domain.tech_contacts << contact
+
+    assert domain.invalid?
   end
 
   def test_validates_name_server_count_when_name_servers_are_required