proxy lazy resolve progress

include/matador/sql/query_result.hpp

@@ -129,10 +129,15 @@ public:
 
 public:
   explicit query_result(std::unique_ptr<query_result_impl> &&impl)
-  : impl_(std::move(impl)) {}
+  : impl_(std::move(impl))
+  , creator_([this]{ return detail::create_prototype<Type>(impl_->prototype()); }  ) {}
+
+  query_result(std::unique_ptr<query_result_impl> &&impl, creator_func&& creator)
+  : impl_(std::move(impl))
+  , creator_(std::move(creator)) {}
 
   iterator begin() { return std::move(++iterator(this)); }
-  iterator end() { return {}; }
+  static iterator end() { return {}; }
 
 private:
   friend class query_result_iterator<Type>;
@@ -143,12 +148,14 @@ private:
 
 protected:
   std::unique_ptr<query_result_impl> impl_;
+  creator_func creator_;
 };
 
 template<typename Type>
 Type *query_result<Type>::create() {
-  return detail::create_prototype<Type>(impl_->prototype());
+  return creator_();
 }
+
 template<typename Type>
 void query_result<Type>::bind(const Type &obj) {
   impl_->bind(obj);