explicitly state PersistentVolume#parent is an Ems

this allows us to define a virtual attribute delegation

|     ms |query | qry ms |     rows |` comments`
|    ---:|  ---:|   ---:|      ---:|  ---
|  278.6 |   31 |  12.7 |       48 |` /persistent_volume/report_data#before`
|  258.7 |   11 |   9.9 |       28 |` /persistent_volume/report_data#after`
|   7.1% |   65%|  22.0%|      42% | diff

app/models/persistent_volume.rb

@@ -2,12 +2,16 @@ class PersistentVolume < ContainerVolume
   acts_as_miq_taggable
   include NewWithTypeStiMixin
   serialize :capacity, Hash
-  delegate :name, :to => :parent, :prefix => true, :allow_nil => true
+
+  # NOTE: overriding parent polymorphic. Ensuring the type gets set
+  belongs_to :parent, :class_name => 'ExtManagementSystem'
+  default_value_for :parent_type, 'ExtManagementSystem'
+
   has_many :container_volumes, -> { where(:type => 'ContainerVolume') }, :through => :persistent_volume_claim
   has_many :parents, -> { distinct }, :through => :container_volumes, :source_type => 'ContainerGroup'
   alias_attribute :container_groups, :parents
 
-  virtual_attribute :parent_name, :string
+  virtual_delegate :name, :to => :parent, :prefix => true, :allow_nil => true, :type => :string
   virtual_attribute :storage_capacity, :string
 
   def storage_capacity

spec/models/persistent_volume_spec.rb

@@ -63,6 +63,6 @@
     end
 
     # delegating through a polymorphic forces us to ruby only
-    it_behaves_like "ruby only virtual_attribute", :parent_name, 'ems_name'
+    it_behaves_like "sql friendly virtual_attribute", :parent_name, 'ems_name'
   end
 end