[C++] Support mapping types for RowEncodeTrait

src/fury/encoder/row_encode_trait.h

@@ -19,6 +19,7 @@
 #include "fury/meta/field_info.h"
 #include "fury/meta/type_traits.h"
 #include "fury/row/writer.h"
+#include <memory>
 #include <string_view>
 #include <type_traits>
 #include <utility>
@@ -67,16 +68,20 @@ template <typename T>
 inline constexpr bool IsString =
     meta::IsOneOf<T, std::string, std::string_view>::value;
 
+template <typename T> inline constexpr bool IsMap = meta::IsPairIterable<T>;
+
 template <typename T>
-inline constexpr bool IsArray = meta::IsIterable<T> && !IsString<T>;
+inline constexpr bool IsArray =
+    meta::IsIterable<T> && !IsString<T> && !IsMap<T>;
 
 template <typename> inline constexpr bool IsOptional = false;
 
 template <typename T> inline constexpr bool IsOptional<std::optional<T>> = true;
 
 template <typename T>
 inline constexpr bool IsClassButNotBuiltin =
-    std::is_class_v<T> && !(IsString<T> || IsArray<T> || IsOptional<T>);
+    std::is_class_v<T> &&
+    !(IsString<T> || IsArray<T> || IsOptional<T> || IsMap<T>);
 
 inline decltype(auto) GetChildType(RowWriter &writer, int index) {
   return writer.schema()->field(index)->type();
@@ -263,6 +268,74 @@ struct RowEncodeTrait<T,
   }
 };
 
+template <typename T>
+struct RowEncodeTrait<T,
+                      std::enable_if_t<details::IsMap<std::remove_cv_t<T>>>> {
+  static auto Type() {
+    return arrow::map(
+        RowEncodeTrait<typename T::value_type::first_type>::Type(),
+        RowEncodeTrait<typename T::value_type::second_type>::Type());
+  }
+
+  template <typename V>
+  static void WriteKey(V &&visitor, const T &value, ArrayWriter &writer) {
+    int index = 0;
+    for (const auto &v : value) {
+      RowEncodeTrait<typename T::value_type::first_type>::Write(
+          std::forward<V>(visitor), v.first, writer, index);
+      ++index;
+    }
+  }
+
+  template <typename V>
+  static void WriteValue(V &&visitor, const T &value, ArrayWriter &writer) {
+    int index = 0;
+    for (const auto &v : value) {
+      RowEncodeTrait<typename T::value_type::second_type>::Write(
+          std::forward<V>(visitor), v.second, writer, index);
+      ++index;
+    }
+  }
+
+  template <typename V, typename W,
+            std::enable_if_t<meta::IsOneOf<W, RowWriter, ArrayWriter>::value,
+                             int> = 0>
+  static void Write(V &&visitor, const T &value, W &writer, int index) {
+    auto offset = writer.cursor();
+    writer.WriteDirectly(-1);
+
+    auto map_type = std::dynamic_pointer_cast<arrow::MapType>(
+        details::GetChildType(writer, index));
+
+    auto key_writer =
+        std::make_unique<ArrayWriter>(std::static_pointer_cast<arrow::ListType>(
+                                          arrow::list(map_type->key_type())),
+                                      &writer);
+
+    key_writer->Reset(value.size());
+    RowEncodeTrait<T>::WriteKey(std::forward<V>(visitor), value,
+                                *key_writer.get());
+
+    writer.WriteDirectly(offset, key_writer->size());
+
+    auto value_writer =
+        std::make_unique<ArrayWriter>(std::static_pointer_cast<arrow::ListType>(
+                                          arrow::list(map_type->item_type())),
+                                      &writer);
+
+    value_writer->Reset(value.size());
+    RowEncodeTrait<T>::WriteValue(std::forward<V>(visitor), value,
+                                  *value_writer.get());
+
+    writer.SetOffsetAndSize(index, offset, writer.cursor() - offset);
+
+    std::forward<V>(visitor).template Visit<std::remove_cv_t<T>>(
+        std::move(key_writer));
+    std::forward<V>(visitor).template Visit<std::remove_cv_t<T>>(
+        std::move(value_writer));
+  }
+};
+
 } // namespace encoder
 
 } // namespace fury

src/fury/encoder/row_encode_trait_test.cc

@@ -294,6 +294,70 @@ TEST(RowEncodeTrait, Optional) {
   }
 }
 
+struct G {
+  std::map<int, std::map<int, int>> a;
+  std::map<std::string, A> b;
+};
+
+FURY_FIELD_INFO(G, a, b);
+
+TEST(RowEncodeTrait, Map) {
+  G v{{{1, {{3, 4}, {5, 6}}}, {2, {{7, 8}, {9, 10}, {11, 12}}}},
+      {{"a", A{1, 1.1, true}}, {"b", A{2, 3.3, false}}}};
+
+  auto schema = encoder::RowEncodeTrait<G>::Type();
+
+  auto a_map =
+      std::dynamic_pointer_cast<arrow::MapType>(schema->field(0)->type());
+  ASSERT_EQ(a_map->key_type()->name(), "int32");
+  ASSERT_EQ(a_map->item_type()->name(), "map");
+  ASSERT_EQ(std::dynamic_pointer_cast<arrow::MapType>(a_map->item_type())
+                ->key_type()
+                ->name(),
+            "int32");
+  ASSERT_EQ(std::dynamic_pointer_cast<arrow::MapType>(a_map->item_type())
+                ->item_type()
+                ->name(),
+            "int32");
+
+  auto b_map =
+      std::dynamic_pointer_cast<arrow::MapType>(schema->field(1)->type());
+  ASSERT_EQ(b_map->key_type()->name(), "utf8");
+  ASSERT_EQ(b_map->item_type()->name(), "struct");
+  ASSERT_EQ(b_map->item_type()->field(0)->type()->name(), "int32");
+  ASSERT_EQ(b_map->item_type()->field(1)->type()->name(), "float");
+  ASSERT_EQ(b_map->item_type()->field(2)->type()->name(), "bool");
+
+  RowWriter writer(encoder::RowEncodeTrait<G>::Schema());
+  writer.Reset();
+
+  encoder::RowEncodeTrait<G>::Write(encoder::EmptyWriteVisitor{}, v, writer);
+
+  auto map_a = writer.ToRow()->GetMap(0);
+  ASSERT_EQ(map_a->keys_array()->GetInt32(0), 1);
+  ASSERT_EQ(map_a->keys_array()->GetInt32(1), 2);
+  ASSERT_EQ(map_a->values_array()->GetMap(0)->keys_array()->GetInt32(0), 3);
+  ASSERT_EQ(map_a->values_array()->GetMap(0)->keys_array()->GetInt32(1), 5);
+  ASSERT_EQ(map_a->values_array()->GetMap(0)->values_array()->GetInt32(0), 4);
+  ASSERT_EQ(map_a->values_array()->GetMap(0)->values_array()->GetInt32(1), 6);
+  ASSERT_EQ(map_a->values_array()->GetMap(1)->keys_array()->GetInt32(0), 7);
+  ASSERT_EQ(map_a->values_array()->GetMap(1)->keys_array()->GetInt32(1), 9);
+  ASSERT_EQ(map_a->values_array()->GetMap(1)->keys_array()->GetInt32(2), 11);
+  ASSERT_EQ(map_a->values_array()->GetMap(1)->values_array()->GetInt32(0), 8);
+  ASSERT_EQ(map_a->values_array()->GetMap(1)->values_array()->GetInt32(1), 10);
+  ASSERT_EQ(map_a->values_array()->GetMap(1)->values_array()->GetInt32(2), 12);
+
+  auto map_b = writer.ToRow()->GetMap(1);
+  ASSERT_EQ(map_b->keys_array()->GetString(0), "a");
+  ASSERT_EQ(map_b->keys_array()->GetString(1), "b");
+  ASSERT_EQ(map_b->values_array()->GetStruct(0)->GetInt32(0), 1);
+  ASSERT_EQ(map_b->values_array()->GetStruct(1)->GetInt32(0), 2);
+  ASSERT_FLOAT_EQ(map_b->values_array()->GetStruct(0)->GetFloat(1), 1.1);
+  ASSERT_FLOAT_EQ(map_b->values_array()->GetStruct(1)->GetFloat(1), 3.3);
+  ASSERT_EQ(map_b->values_array()->GetStruct(0)->GetBoolean(2), true);
+  ASSERT_EQ(map_b->values_array()->GetStruct(1)->GetBoolean(2), false);
+}
+
 } // namespace test
 
 } // namespace fury

src/fury/meta/type_traits.h

@@ -97,6 +97,26 @@ constexpr inline bool IsIterable =
 template <typename T>
 using GetValueType = typename details::GetValueTypeImpl<T>::type;
 
+namespace details {
+
+template <typename> constexpr inline bool IsPair = false;
+
+template <typename T1, typename T2>
+constexpr inline bool IsPair<std::pair<T1, T2>> = true;
+
+template <typename> std::false_type IsPairIterableImpl(...);
+
+template <
+    typename T,
+    std::enable_if_t<IsIterable<T> && IsPair<typename T::value_type>, int> = 0>
+std::true_type IsPairIterableImpl(int);
+
+} // namespace details
+
+template <typename T>
+constexpr inline bool IsPairIterable =
+    decltype(details::IsPairIterableImpl<T>(0))::value;
+
 } // namespace meta
 
 } // namespace fury

src/fury/meta/type_traits_test.cc

@@ -18,6 +18,8 @@
 #include <deque>
 #include <initializer_list>
 #include <list>
+#include <queue>
+#include <type_traits>
 
 #include "fury/meta/field_info.h"
 #include "src/fury/meta/type_traits.h"
@@ -64,6 +66,11 @@ TEST(Meta, IsUnique) {
 }
 
 TEST(Meta, IsIterable) {
+  static_assert(!IsIterable<int>);
+  static_assert(!IsIterable<const bool>);
+  static_assert(!IsIterable<int &>);
+  static_assert(!IsIterable<std::false_type>);
+  static_assert(!IsIterable<std::queue<int>>);
   static_assert(IsIterable<std::vector<int>>);
   static_assert(IsIterable<std::vector<std::vector<int>>>);
   static_assert(IsIterable<std::deque<float>>);
@@ -77,6 +84,20 @@ TEST(Meta, IsIterable) {
   static_assert(IsIterable<std::string_view>);
 }
 
+TEST(Meta, IsPairIterable) {
+  static_assert(!IsPairIterable<int>);
+  static_assert(!IsPairIterable<std::string>);
+  static_assert(!IsPairIterable<std::vector<int>>);
+  static_assert(!IsPairIterable<std::vector<std::vector<int>>>);
+  static_assert(!IsPairIterable<std::deque<float>>);
+  static_assert(!IsPairIterable<std::list<int>>);
+  static_assert(!IsPairIterable<std::set<int>>);
+  static_assert(IsPairIterable<std::map<int, std::vector<unsigned>>>);
+  static_assert(IsPairIterable<std::map<std::string, int>>);
+  static_assert(IsPairIterable<std::multimap<std::string, bool>>);
+  static_assert(IsPairIterable<std::unordered_map<std::string, float>>);
+}
+
 } // namespace test
 
 } // namespace fury