From 93ed3cae58a8a6e8f32479c788ca4126cdb0c4d1 Mon Sep 17 00:00:00 2001
From: Sutou Kouhei <kou@clear-code.com>
Date: Fri, 23 Aug 2024 14:32:07 +0900
Subject: [PATCH] GH-43797: [C++] Attach `arrow::ArrayStatistics` to
 `arrow::ArrayData`

If we can attach associated statistics to an array via `ArrayData`, we
can use it in later processes such as query planning.
---
 cpp/src/arrow/array/array_base.h |  8 ++++++++
 cpp/src/arrow/array/data.h       | 12 ++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/cpp/src/arrow/array/array_base.h b/cpp/src/arrow/array/array_base.h
index 716ae0722069e..c36d4518bdbd9 100644
--- a/cpp/src/arrow/array/array_base.h
+++ b/cpp/src/arrow/array/array_base.h
@@ -232,6 +232,14 @@ class ARROW_EXPORT Array {
   /// \return DeviceAllocationType
   DeviceAllocationType device_type() const { return data_->device_type(); }
 
+  /// \brief Return the statistics of this Array
+  ///
+  /// This just delegates to calling statistics on the underlying ArrayData
+  /// object which backs this Array.
+  ///
+  /// \return const ArrayStatistics&
+  const ArrayStatistics& statistics() const { return data_->statistics; }
+
  protected:
   Array() = default;
   ARROW_DEFAULT_MOVE_AND_ASSIGN(Array);
diff --git a/cpp/src/arrow/array/data.h b/cpp/src/arrow/array/data.h
index e0508fe6980a7..14eaed67e71d7 100644
--- a/cpp/src/arrow/array/data.h
+++ b/cpp/src/arrow/array/data.h
@@ -24,6 +24,7 @@
 #include <utility>
 #include <vector>
 
+#include "arrow/array/statistics.h"
 #include "arrow/buffer.h"
 #include "arrow/result.h"
 #include "arrow/type.h"
@@ -152,7 +153,8 @@ struct ARROW_EXPORT ArrayData {
         offset(other.offset),
         buffers(std::move(other.buffers)),
         child_data(std::move(other.child_data)),
-        dictionary(std::move(other.dictionary)) {
+        dictionary(std::move(other.dictionary)),
+        statistics(std::move(other.statistics)) {
     SetNullCount(other.null_count);
   }
 
@@ -163,7 +165,8 @@ struct ARROW_EXPORT ArrayData {
         offset(other.offset),
         buffers(other.buffers),
         child_data(other.child_data),
-        dictionary(other.dictionary) {
+        dictionary(other.dictionary),
+        statistics(other.statistics) {
     SetNullCount(other.null_count);
   }
 
@@ -176,6 +179,7 @@ struct ARROW_EXPORT ArrayData {
     buffers = std::move(other.buffers);
     child_data = std::move(other.child_data);
     dictionary = std::move(other.dictionary);
+    statistics = std::move(other.statistics);
     return *this;
   }
 
@@ -188,6 +192,7 @@ struct ARROW_EXPORT ArrayData {
     buffers = other.buffers;
     child_data = other.child_data;
     dictionary = other.dictionary;
+    statistics = other.statistics;
     return *this;
   }
 
@@ -390,6 +395,9 @@ struct ARROW_EXPORT ArrayData {
 
   // The dictionary for this Array, if any. Only used for dictionary type
   std::shared_ptr<ArrayData> dictionary;
+
+  // The statistics for this Array.
+  ArrayStatistics statistics{};
 };
 
 /// \brief A non-owning Buffer reference