From f6e8958382bc6dc314a87a8fd7dc11ffa96a1162 Mon Sep 17 00:00:00 2001
From: Junming Chen <junming.chen.r@outlook.com>
Date: Mon, 13 Nov 2023 00:05:27 +0800
Subject: [PATCH] add test

---
 cpp/src/arrow/array/array_dict.cc      | 15 +++++-----
 cpp/src/arrow/array/array_dict_test.cc | 41 ++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/cpp/src/arrow/array/array_dict.cc b/cpp/src/arrow/array/array_dict.cc
index 0b714ddc2b9ee..ee0d14c24b41b 100644
--- a/cpp/src/arrow/array/array_dict.cc
+++ b/cpp/src/arrow/array/array_dict.cc
@@ -212,12 +212,12 @@ Result<std::shared_ptr<ArrayData>> TransposeDictIndices(
   return out_data;
 }
 
-struct CompactDictionaryNullValuesVistor {
+struct CountDictionaryNullValuesVistor {
   const std::shared_ptr<ArrayData>& data;
   int64_t& out_null_count;
 
   template <typename IndexArrowType>
-  Status CompactDictionaryNullValuesImpl() {
+  Status CountDictionaryNullValuesImpl() {
     int64_t index_length = data->length;
     int64_t dict_length = data->dictionary->length;
     const uint8_t* dictionary_null_bit_map = data->dictionary->GetValues<uint8_t>(0);
@@ -245,7 +245,7 @@ struct CompactDictionaryNullValuesVistor {
 
   template <typename Type>
   enable_if_integer<Type, Status> Visit(const Type&) {
-    return CompactDictionaryNullValuesImpl<Type>();
+    return CountDictionaryNullValuesImpl<Type>();
   }
 
   Status Visit(const DataType& type) {
@@ -253,10 +253,10 @@ struct CompactDictionaryNullValuesVistor {
   }
 };
 
-Result<int64_t> CompactDictionaryNullValues(const std::shared_ptr<ArrayData>& data) {
+Result<int64_t> CountDictionaryNullValues(const std::shared_ptr<ArrayData>& data) {
   int64_t out_null_count = 0;
   const auto& dict_type = checked_cast<const DictionaryType&>(*data->type);
-  CompactDictionaryNullValuesVistor vistor{data, out_null_count};
+  CountDictionaryNullValuesVistor vistor{data, out_null_count};
   RETURN_NOT_OK(VisitTypeInline(*dict_type.index_type(), &vistor));
 
   return out_null_count;
@@ -374,12 +374,11 @@ Result<std::shared_ptr<Array>> DictionaryArray::Transpose(
 }
 
 Result<int64_t> DictionaryArray::CountNullValues() const {
-  if (this->dictionary()->null_count() == 0 || this->indices()->null_count() == 0) {
+  if (this->dictionary()->null_count() == 0 || this->indices()->length() == 0) {
     return this->indices()->null_count();
   }
 
-  ARROW_ASSIGN_OR_RAISE(int64_t dictionary_null_count,
-                        CompactDictionaryNullValues(data_));
+  ARROW_ASSIGN_OR_RAISE(int64_t dictionary_null_count, CountDictionaryNullValues(data_));
   return dictionary_null_count + this->indices()->null_count();
 }
 
diff --git a/cpp/src/arrow/array/array_dict_test.cc b/cpp/src/arrow/array/array_dict_test.cc
index 2f3ee6e2d49a5..87821a52c7637 100644
--- a/cpp/src/arrow/array/array_dict_test.cc
+++ b/cpp/src/arrow/array/array_dict_test.cc
@@ -1428,6 +1428,47 @@ TEST(TestDictionary, IndicesArray) {
   ASSERT_OK(arr->indices()->ValidateFull());
 }
 
+void CheckDictionaryComputeNullValues(const std::shared_ptr<DataType>& dict_type,
+                                      const std::string& input_dictionary_json,
+                                      const std::string& input_index_json,
+                                      const int64_t& expected_null_count) {
+  auto input = DictArrayFromJSON(dict_type, input_index_json, input_dictionary_json);
+  const DictionaryArray& input_ref = checked_cast<const DictionaryArray&>(*input);
+
+  ASSERT_OK_AND_ASSIGN(int64_t actual, input_ref.CountNullValues());
+  ASSERT_EQ(expected_null_count, actual);
+}
+
+TEST(TestDictionary, ComputeNullValues) {
+  std::shared_ptr<arrow::DataType> type;
+  std::shared_ptr<arrow::DataType> dict_type;
+
+  for (const auto& index_type : all_dictionary_index_types()) {
+    ARROW_SCOPED_TRACE("index_type = ", index_type->ToString());
+
+    type = boolean();
+    dict_type = dictionary(index_type, type);
+
+    // no null value
+    CheckDictionaryComputeNullValues(dict_type, "[]", "[]", 0);
+    CheckDictionaryComputeNullValues(dict_type, "[true, false]", "[0, 1, 0]", 0);
+
+    // only indices contain null value
+    CheckDictionaryComputeNullValues(dict_type, "[true, false]", "[null, 0, 1]", 1);
+    CheckDictionaryComputeNullValues(dict_type, "[true, false]", "[null, null]", 2);
+
+    // only dictionary contains null value
+    CheckDictionaryComputeNullValues(dict_type, "[null, true]", "[]", 0);
+    CheckDictionaryComputeNullValues(dict_type, "[null, true, false]", "[0, 1, 0]", 2);
+
+    // both indices and dictionary contain null value
+    CheckDictionaryComputeNullValues(dict_type, "[null, true, false]", "[0, 1, 0, null]",
+                                     3);
+    CheckDictionaryComputeNullValues(dict_type, "[null, true, null, false]",
+                                     "[null, 1, 0, 2, 3]", 3);
+  }
+}
+
 void CheckDictionaryCompact(const std::shared_ptr<DataType>& dict_type,
                             const std::string& input_dictionary_json,
                             const std::string& input_index_json,