Micro optimizations

Author: taehyounpark

include/queryosity/column.h

@@ -94,7 +94,7 @@ template <typename T> class variable {
 public:
   variable() = default;
   template <typename U> variable(view<U> const &val);
-  virtual ~variable() = default;
+  ~variable() = default;
 
   variable(variable &&) = default;
   variable &operator=(variable &&) = default;
@@ -117,7 +117,7 @@ template <typename Val> class observable {
    * @brief Constructor out of a variable.
    */
   observable(variable<Val> const &obs);
-  virtual ~observable() = default;
+  ~observable() = default;
 
   /**
    * @brief Compute and retrieve the value of the column.

include/queryosity/lazy.h

@@ -429,14 +429,14 @@ void queryosity::lazy<Action>::merge_results() {
   using result_type = decltype(model->result());
   const auto nslots = this->size();
   if (nslots == 1) {
-    this->m_result = model->result();
+    this->m_result = std::move(model->result());
   } else {
     std::vector<result_type> results;
     results.reserve(nslots);
     for (size_t islot = 0; islot < nslots; ++islot) {
       results.push_back(std::move(this->get_slot(islot)->result()));
     }
-    this->m_result = model->merge(results);
+    this->m_result = std::move(model->merge(results));
   }
   this->m_merged = true;
 }