TypedValue getters return references

Reviewers: buda

Reviewed By: buda

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D113

src/query/backend/cpp/typed_value.cpp

@@ -1,7 +1,7 @@
 #include "query/backend/cpp/typed_value.hpp"
 
-#include <fmt/format.h>
 #include <cmath>
+#include <fmt/format.h>
 #include <iostream>
 #include <memory>
 
@@ -61,32 +61,28 @@ TypedValue::operator PropertyValue() const {
 // Other solution would be to add additional overloads for references, for
 // example Value<string&>.
 // Value extraction template instantiations
-template <>
-bool TypedValue::Value<bool>() const {
+template <> const bool &TypedValue::Value<bool>() const {
   if (type_ != TypedValue::Type::Bool) {
     throw TypedValueException("Incompatible template param and type");
   }
   return bool_v;
 }
 
-template <>
-int64_t TypedValue::Value<int64_t>() const {
+template <> const int64_t &TypedValue::Value<int64_t>() const {
   if (type_ != TypedValue::Type::Int) {
     throw TypedValueException("Incompatible template param and type");
   }
   return int_v;
 }
 
-template <>
-double TypedValue::Value<double>() const {
+template <> const double &TypedValue::Value<double>() const {
   if (type_ != TypedValue::Type::Double) {
     throw TypedValueException("Incompatible template param and type");
   }
   return double_v;
 }
 
-template <>
-std::string TypedValue::Value<std::string>() const {
+template <> const std::string &TypedValue::Value<std::string>() const {
   if (type_ != TypedValue::Type::String) {
     throw TypedValueException("Incompatible template param and type");
   }
@@ -94,7 +90,8 @@ std::string TypedValue::Value<std::string>() const {
 }
 
 template <>
-std::vector<TypedValue> TypedValue::Value<std::vector<TypedValue>>() const {
+const std::vector<TypedValue> &
+TypedValue::Value<std::vector<TypedValue>>() const {
   if (type_ != TypedValue::Type::List) {
     throw TypedValueException("Incompatible template param and type");
   }
@@ -102,7 +99,7 @@ std::vector<TypedValue> TypedValue::Value<std::vector<TypedValue>>() const {
 }
 
 template <>
-std::map<std::string, TypedValue>
+std::map<std::string, TypedValue> const &
 TypedValue::Value<std::map<std::string, TypedValue>>() const {
   if (type_ != TypedValue::Type::Map) {
     throw TypedValueException("Incompatible template param and type");
@@ -110,24 +107,87 @@ TypedValue::Value<std::map<std::string, TypedValue>>() const {
   return map_v;
 }
 
-template <>
-VertexAccessor TypedValue::Value<VertexAccessor>() const {
+template <> const VertexAccessor &TypedValue::Value<VertexAccessor>() const {
   if (type_ != TypedValue::Type::Vertex) {
     throw TypedValueException("Incompatible template param and type");
   }
   return vertex_v;
 }
 
-template <>
-EdgeAccessor TypedValue::Value<EdgeAccessor>() const {
+template <> const EdgeAccessor &TypedValue::Value<EdgeAccessor>() const {
   if (type_ != TypedValue::Type::Edge) {
     throw TypedValueException("Incompatible template param and type");
   }
   return edge_v;
 }
 
+template <> const Path &TypedValue::Value<Path>() const {
+  if (type_ != TypedValue::Type::Path) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return path_v;
+}
+
+template <> bool &TypedValue::Value<bool>() {
+  if (type_ != TypedValue::Type::Bool) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return bool_v;
+}
+
+template <> int64_t &TypedValue::Value<int64_t>() {
+  if (type_ != TypedValue::Type::Int) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return int_v;
+}
+
+template <> double &TypedValue::Value<double>() {
+  if (type_ != TypedValue::Type::Double) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return double_v;
+}
+
+template <> std::string &TypedValue::Value<std::string>() {
+  if (type_ != TypedValue::Type::String) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return string_v;
+}
+
 template <>
-Path TypedValue::Value<Path>() const {
+std::vector<TypedValue> &TypedValue::Value<std::vector<TypedValue>>() {
+  if (type_ != TypedValue::Type::List) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return list_v;
+}
+
+template <>
+std::map<std::string, TypedValue> &
+TypedValue::Value<std::map<std::string, TypedValue>>() {
+  if (type_ != TypedValue::Type::Map) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return map_v;
+}
+
+template <> VertexAccessor &TypedValue::Value<VertexAccessor>() {
+  if (type_ != TypedValue::Type::Vertex) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return vertex_v;
+}
+
+template <> EdgeAccessor &TypedValue::Value<EdgeAccessor>() {
+  if (type_ != TypedValue::Type::Edge) {
+    throw TypedValueException("Incompatible template param and type");
+  }
+  return edge_v;
+}
+
+template <> Path &TypedValue::Value<Path>() {
   if (type_ != TypedValue::Type::Path) {
     throw TypedValueException("Incompatible template param and type");
   }
@@ -370,7 +430,8 @@ TypedValue operator==(const TypedValue& a, const TypedValue& b) {
       // can compare list_v-s directly.
       auto list1 = a.Value<std::vector<TypedValue>>();
       auto list2 = b.Value<std::vector<TypedValue>>();
-      if (list1.size() != list2.size()) return false;
+      if (list1.size() != list2.size())
+        return false;
       for (int i = 0; i < (int)list1.size(); ++i) {
         if (!(list1[i] == list2[i]).Value<bool>()) {
           return false;
@@ -481,7 +542,8 @@ inline void EnsureArithmeticallyOk(const TypedValue& a, const TypedValue& b,
     throw TypedValueException("Invalid {} operand types {}, {}", op_name,
                               a.type(), b.type());
 
-  if (string_ok) return;
+  if (string_ok)
+    return;
 
   if (a.type() == TypedValue::Type::String ||
       b.type() == TypedValue::Type::String)

src/query/backend/cpp/typed_value.hpp

@@ -1,19 +1,19 @@
 #pragma once
 
+#include <cstdint>
 #include <iostream>
+#include <map>
 #include <memory>
 #include <string>
 #include <vector>
-#include <map>
-#include <cstdint>
 
+#include "storage/edge_accessor.hpp"
+#include "storage/property_value.hpp"
+#include "storage/vertex_accessor.hpp"
+#include "traversal/path.hpp"
 #include "utils/exceptions/stacktrace_exception.hpp"
 #include "utils/total_ordering.hpp"
 #include "utils/underlying_cast.hpp"
-#include "storage/property_value.hpp"
-#include "storage/edge_accessor.hpp"
-#include "storage/vertex_accessor.hpp"
-#include "traversal/path.hpp"
 
 typedef traversal_template::Path<VertexAccessor, EdgeAccessor> Path;
 
@@ -95,8 +95,8 @@ class TypedValue : public TotalOrdering<TypedValue, TypedValue, TypedValue> {
    * @tparam T Type to interpret the value as.
    * @return The value as type T.
    */
-  template <typename T>
-  T Value() const;
+  template <typename T> T &Value();
+  template <typename T> const T &Value() const;
 
   friend std::ostream &operator<<(std::ostream &stream, const TypedValue &prop);