finished statement cache class

source/orm/sql/interface/statement_proxy.cpp

@@ -15,6 +15,10 @@ void statement_proxy::reset() const {
   statement_->reset();
 }
 
+std::string statement_proxy::sql() const {
+  return statement_->query_.sql;
+}
+
 std::unique_ptr<utils::attribute_writer> statement_proxy::create_binder() const {
   return statement_->create_binder();
 }