feat: introduce specialized API to write fixed length data rapidly (#…

…5181) close #5183
pingcap · Jun 24, 2022 · 73e708c · 73e708c
1 parent dab31a5
commit 73e708c
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Showing 2 changed files with 22 additions and 4 deletions.
diff --git 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_)
@@ -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();
 }

diff --git 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)
     {