From 74164e777065c1ceacd8a13322f6d50ccaeecfa0 Mon Sep 17 00:00:00 2001
From: SchrodingerZhu <i@zhuyi.fan>
Date: Tue, 21 Jun 2022 19:19:37 +0800
Subject: [PATCH 1/2] feat: introduce specilized API to write fixed length data
 rapidly

Signed-off-by: SchrodingerZhu <i@zhuyi.fan>
---
 dbms/src/Flash/Coprocessor/TiDBColumn.cpp |  2 +-
 dbms/src/IO/WriteBuffer.h                 | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/dbms/src/Flash/Coprocessor/TiDBColumn.cpp b/dbms/src/Flash/Coprocessor/TiDBColumn.cpp
index 7183374a5c1..b8501c02b55 100644
--- a/dbms/src/Flash/Coprocessor/TiDBColumn.cpp
+++ b/dbms/src/Flash/Coprocessor/TiDBColumn.cpp
@@ -28,7 +28,7 @@ template <typename T>
 void encodeLittleEndian(const T & value, WriteBuffer & ss)
 {
     auto v = toLittleEndian(value);
-    ss.write(reinterpret_cast<const char *>(&v), sizeof(v));
+    ss.template writeFixed<T>(&v);
 }
 
 TiDBColumn::TiDBColumn(Int8 element_len_)
diff --git a/dbms/src/IO/WriteBuffer.h b/dbms/src/IO/WriteBuffer.h
index 361081d1176..0c0fa2cb545 100644
--- a/dbms/src/IO/WriteBuffer.h
+++ b/dbms/src/IO/WriteBuffer.h
@@ -96,6 +96,24 @@ class WriteBuffer : public BufferBase
         }
     }
 
+    template <class T>
+    __attribute__((always_inline)) void writeFixed(const T * __restrict from)
+    {
+        if (likely(working_buffer.end() - pos >= static_cast<ptrdiff_t>(sizeof(T))))
+        {
+            tiflash_compiler_builtin_memcpy(pos, from, sizeof(T));
+            pos += sizeof(T);
+        }
+        else
+        {
+            [&]() __attribute__((noinline))
+            {
+                write(reinterpret_cast<const char *>(from), sizeof(T));
+            }
+            ();
+        }
+    }
+
 
     inline void write(char x)
     {

From 2b4eead7b207b78241e8f02526ce9175ba774119 Mon Sep 17 00:00:00 2001
From: SchrodingerZhu <i@zhuyi.fan>
Date: Tue, 21 Jun 2022 19:41:50 +0800
Subject: [PATCH 2/2] chore: tidy up TiDBColumn

Signed-off-by: SchrodingerZhu <i@zhuyi.fan>
---
 dbms/src/Flash/Coprocessor/TiDBColumn.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/dbms/src/Flash/Coprocessor/TiDBColumn.cpp b/dbms/src/Flash/Coprocessor/TiDBColumn.cpp
index b8501c02b55..eef89696d3a 100644
--- a/dbms/src/Flash/Coprocessor/TiDBColumn.cpp
+++ b/dbms/src/Flash/Coprocessor/TiDBColumn.cpp
@@ -141,10 +141,10 @@ void TiDBColumn::append(const TiDBDecimal & decimal)
     encodeLittleEndian<UInt8>(decimal.digits_int, *data);
     encodeLittleEndian<UInt8>(decimal.digits_frac, *data);
     encodeLittleEndian<UInt8>(decimal.result_frac, *data);
-    encodeLittleEndian<UInt8>((UInt8)decimal.negative, *data);
-    for (int i = 0; i < MAX_WORD_BUF_LEN; i++)
+    encodeLittleEndian<UInt8>(static_cast<UInt8>(decimal.negative), *data);
+    for (int i : decimal.word_buf)
     {
-        encodeLittleEndian<Int32>(decimal.word_buf[i], *data);
+        encodeLittleEndian<Int32>(i, *data);
     }
     finishAppendFixed();
 }