From 29a3c3a74f96497fefb2027fcf6d89656a827603 Mon Sep 17 00:00:00 2001
From: Yuya Asano <64895419+sukeya@users.noreply.github.com>
Date: Wed, 11 Feb 2026 12:17:49 +0900
Subject: [PATCH] Optimize btree value shifts for trivially copyable types

---
 benchmark/btree_bench.cpp                     |  9 ++++++++
 include/platanus/internal/btree_base_node.hpp | 21 +++++++++++++++++--
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/benchmark/btree_bench.cpp b/benchmark/btree_bench.cpp
index d362d74..a81d19b 100644
--- a/benchmark/btree_bench.cpp
+++ b/benchmark/btree_bench.cpp
@@ -296,9 +296,18 @@ using STLMultiMap = std::multimap<T, T>;
   REGISTER_BENCHMARK_FUNCTIONS(container, std::int64_t); \
   REGISTER_BENCHMARK_FUNCTIONS(container, std::string);
 
+#define REGISTER_TRIVIAL_SHIFT_BENCHMARKS(container, type) \
+  STL_AND_BTREE_BENCHMARK(container, type, Insert);         \
+  STL_AND_BTREE_BENCHMARK(container, type, Delete);
+
 REGISTER_BENCHMARK_TYPES(Set);
 REGISTER_BENCHMARK_TYPES(MultiSet);
 REGISTER_BENCHMARK_TYPES(Map);
 REGISTER_BENCHMARK_TYPES(MultiMap);
 
+REGISTER_TRIVIAL_SHIFT_BENCHMARKS(Set, int);
+REGISTER_TRIVIAL_SHIFT_BENCHMARKS(Set, std::pair<int, int>);
+REGISTER_TRIVIAL_SHIFT_BENCHMARKS(Map, int);
+REGISTER_TRIVIAL_SHIFT_BENCHMARKS(Map, std::pair<int, int>);
+
 BENCHMARK_MAIN();
diff --git a/include/platanus/internal/btree_base_node.hpp b/include/platanus/internal/btree_base_node.hpp
index 179f790..223a250 100644
--- a/include/platanus/internal/btree_base_node.hpp
+++ b/include/platanus/internal/btree_base_node.hpp
@@ -32,7 +32,10 @@
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
+#include <cstring>
 #include <iterator>
+#include <memory>
+#include <type_traits>
 
 #include "btree_node_fwd.hpp"
 #include "btree_util.hpp"
@@ -287,7 +290,14 @@ class btree_base_node {
     assert(last + shift <= max_values_count());
     auto begin = std::next(begin_values(), first);
     auto end   = std::next(begin_values(), last);
-    std::move_backward(begin, end, std::next(end, shift));
+    if constexpr (std::is_trivially_copyable_v<mutable_value_type>) {
+      auto* src = std::to_address(begin);
+      // std::memmove handles overlapping ranges, so right shifts (destination starts inside source)
+      // remain well-defined for trivially copyable values.
+      std::memmove(src + shift, src, static_cast<std::size_t>(last - first) * sizeof(*src));
+    } else {
+      std::move_backward(begin, end, std::next(end, shift));
+    }
   }
 
   // Shift values from first to last by shift toward left.
@@ -299,7 +309,14 @@ class btree_base_node {
     assert(0 <= first - shift);
     auto begin = std::next(begin_values(), first);
     auto end   = std::next(begin_values(), last);
-    std::move(begin, end, std::prev(begin, shift));
+    if constexpr (std::is_trivially_copyable_v<mutable_value_type>) {
+      auto* src = std::to_address(begin);
+      // std::memmove handles overlapping ranges, so left shifts (destination ends inside source)
+      // remain well-defined for trivially copyable values.
+      std::memmove(src - shift, src, static_cast<std::size_t>(last - first) * sizeof(*src));
+    } else {
+      std::move(begin, end, std::prev(begin, shift));
+    }
   }
 
  private: