From 942f757e8bc0aaa7cf788bdf0c4091b63c9af7e5 Mon Sep 17 00:00:00 2001
From: Sutou Kouhei <kou@clear-code.com>
Date: Fri, 30 Aug 2024 13:37:07 +0900
Subject: [PATCH] Add support for CopyTo

---
 cpp/src/arrow/array/array_test.cc | 18 ++++++++++++++++++
 cpp/src/arrow/array/data.cc       |  2 ++
 2 files changed, 20 insertions(+)

diff --git a/cpp/src/arrow/array/array_test.cc b/cpp/src/arrow/array/array_test.cc
index 930095eb67e7b..73e0c692432b6 100644
--- a/cpp/src/arrow/array/array_test.cc
+++ b/cpp/src/arrow/array/array_test.cc
@@ -3812,6 +3812,24 @@ TEST_F(TestArrayDataStatistics, CopyAssignment) {
   ASSERT_TRUE(copied_data.statistics->is_max_exact);
 }
 
+TEST_F(TestArrayDataStatistics, CopyTo) {
+  ASSERT_OK_AND_ASSIGN(auto copied_data,
+                       data_->CopyTo(arrow::default_cpu_memory_manager()));
+
+  ASSERT_TRUE(copied_data->statistics->null_count.has_value());
+  ASSERT_EQ(null_count_, copied_data->statistics->null_count.value());
+
+  ASSERT_TRUE(copied_data->statistics->min.has_value());
+  ASSERT_TRUE(std::holds_alternative<int64_t>(copied_data->statistics->min.value()));
+  ASSERT_EQ(min_, std::get<int64_t>(copied_data->statistics->min.value()));
+  ASSERT_TRUE(copied_data->statistics->is_min_exact);
+
+  ASSERT_TRUE(copied_data->statistics->max.has_value());
+  ASSERT_TRUE(std::holds_alternative<int64_t>(copied_data->statistics->max.value()));
+  ASSERT_EQ(max_, std::get<int64_t>(copied_data->statistics->max.value()));
+  ASSERT_TRUE(copied_data->statistics->is_max_exact);
+}
+
 TEST_F(TestArrayDataStatistics, Slice) {
   auto sliced_data = data_->Slice(0, 1);
   ASSERT_FALSE(sliced_data->statistics);
diff --git a/cpp/src/arrow/array/data.cc b/cpp/src/arrow/array/data.cc
index ee6b04bfca70f..8e29297a8c175 100644
--- a/cpp/src/arrow/array/data.cc
+++ b/cpp/src/arrow/array/data.cc
@@ -165,6 +165,8 @@ Result<std::shared_ptr<ArrayData>> CopyToImpl(const ArrayData& data,
     ARROW_ASSIGN_OR_RAISE(output->dictionary, CopyToImpl(*data.dictionary, to, copy_fn));
   }
 
+  output->statistics = data.statistics;
+
   return output;
 }
 }  // namespace