added pk information to class object

source/core/object/object.cpp

@@ -21,6 +21,18 @@ void object::add_constraint( class constraint c ) {
   ref.owner_ = this;
 }
 
+const attribute* object::primary_key_attribute() const {
+  return pk_attribute_;
+}
+
+const utils::identifier& object::primary_key() const {
+  return pk_identifier_;
+}
+
+bool object::has_primary_key() const {
+  return pk_attribute_ != nullptr;
+}
+
 const std::string& object::name() const {
   return name_;
 }