From 8d8490ac5805c01b51603eec4333d2326febbece Mon Sep 17 00:00:00 2001
From: ltrk2 <107155950+ltrk2@users.noreply.github.com>
Date: Wed, 23 Aug 2023 11:14:34 -0700
Subject: [PATCH] Implement endianness-independent serialization for UUIDs

---
 .../Serializations/SerializationUUID.cpp      | 25 +++++++++++++------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/DataTypes/Serializations/SerializationUUID.cpp b/src/DataTypes/Serializations/SerializationUUID.cpp
index 93658fd05a3..947394a2bd8 100644
--- a/src/DataTypes/Serializations/SerializationUUID.cpp
+++ b/src/DataTypes/Serializations/SerializationUUID.cpp
@@ -7,6 +7,7 @@
 #include <IO/WriteHelpers.h>
 #include <Common/assert_cast.h>
 
+#include <ranges>
 
 namespace DB
 {
@@ -136,23 +137,31 @@ void SerializationUUID::deserializeBinary(IColumn & column, ReadBuffer & istr, c
 void SerializationUUID::serializeBinaryBulk(const IColumn & column, WriteBuffer & ostr, size_t offset, size_t limit) const
 {
     const typename ColumnVector<UUID>::Container & x = typeid_cast<const ColumnVector<UUID> &>(column).getData();
-
-    size_t size = x.size();
-
-    if (limit == 0 || offset + limit > size)
+    if (const size_t size = x.size(); limit == 0 || offset + limit > size)
         limit = size - offset;
 
-    if (limit)
+    if (limit == 0)
+        return;
+
+    if constexpr (std::endian::native == std::endian::big)
+    {
+        std::ranges::for_each(
+            x | std::views::drop(offset) | std::views::take(limit), [&ostr](const auto & uuid) { writeBinaryLittleEndian(uuid, ostr); });
+    }
+    else
         ostr.write(reinterpret_cast<const char *>(&x[offset]), sizeof(UUID) * limit);
 }
 
 void SerializationUUID::deserializeBinaryBulk(IColumn & column, ReadBuffer & istr, size_t limit, double /*avg_value_size_hint*/) const
 {
     typename ColumnVector<UUID>::Container & x = typeid_cast<ColumnVector<UUID> &>(column).getData();
-    size_t initial_size = x.size();
+    const size_t initial_size = x.size();
     x.resize(initial_size + limit);
-    size_t size = istr.readBig(reinterpret_cast<char*>(&x[initial_size]), sizeof(UUID) * limit);
+    const size_t size = istr.readBig(reinterpret_cast<char *>(&x[initial_size]), sizeof(UUID) * limit);
     x.resize(initial_size + size / sizeof(UUID));
-}
 
+    if constexpr (std::endian::native == std::endian::big)
+        std::ranges::for_each(
+            x | std::views::drop(initial_size), [](auto & uuid) { transformEndianness<std::endian::big, std::endian::little>(uuid); });
+}
 }