From 90c721ad72f44ff5849e131d813509d1dedbe035 Mon Sep 17 00:00:00 2001
From: Shirly <AndreMouche@126.com>
Date: Thu, 19 Jul 2018 18:53:16 +0800
Subject: [PATCH] chunk/codec: adjust decoding offsets in chunk (#7106)

---
 util/chunk/codec.go      |  2 +-
 util/chunk/codec_test.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/util/chunk/codec.go b/util/chunk/codec.go
index 9f9cb07eebf99..a9a3df7587194 100644
--- a/util/chunk/codec.go
+++ b/util/chunk/codec.go
@@ -128,7 +128,7 @@ func (c *Codec) decodeColumn(buffer []byte, col *column, ordinal int) (remained
 	numDataBytes := numFixedBytes * col.length
 	if numFixedBytes == -1 {
 		numOffsetBytes := (col.length + 1) * 4
-		col.offsets = append(col.offsets[:0], c.bytesToI32Slice(buffer)...)
+		col.offsets = append(col.offsets[:0], c.bytesToI32Slice(buffer[:numOffsetBytes])...)
 		buffer = buffer[numOffsetBytes:]
 		numDataBytes = int(col.offsets[col.length])
 	} else if cap(col.elemBuf) < numFixedBytes {
diff --git a/util/chunk/codec_test.go b/util/chunk/codec_test.go
index dfd237a1bd1d5..99aa4027647d1 100644
--- a/util/chunk/codec_test.go
+++ b/util/chunk/codec_test.go
@@ -154,3 +154,36 @@ func BenchmarkDecodeToChunk(b *testing.B) {
 		codec.DecodeToChunk(buffer, chk)
 	}
 }
+
+func BenchmarkDecodeToChunkWithVariableType(b *testing.B) {
+	numCols := 6
+	numRows := 1024
+
+	colTypes := make([]*types.FieldType, 0, numCols)
+	colTypes = append(colTypes, &types.FieldType{Tp: mysql.TypeLonglong})
+	colTypes = append(colTypes, &types.FieldType{Tp: mysql.TypeLonglong})
+	colTypes = append(colTypes, &types.FieldType{Tp: mysql.TypeVarchar})
+	colTypes = append(colTypes, &types.FieldType{Tp: mysql.TypeVarchar})
+	colTypes = append(colTypes, &types.FieldType{Tp: mysql.TypeNewDecimal})
+	colTypes = append(colTypes, &types.FieldType{Tp: mysql.TypeJSON})
+
+	chk := NewChunkWithCapacity(colTypes, numRows)
+	for i := 0; i < numRows; i++ {
+		str := fmt.Sprintf("%d.12345", i)
+		chk.AppendNull(0)
+		chk.AppendInt64(1, int64(i))
+		chk.AppendString(2, str)
+		chk.AppendString(3, str)
+		chk.AppendMyDecimal(4, types.NewDecFromStringForTest(str))
+		chk.AppendJSON(5, json.CreateBinary(str))
+	}
+	codec := &Codec{colTypes}
+	buffer := codec.Encode(chk)
+
+	chk.Reset()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		codec.DecodeToChunk(buffer, chk)
+	}
+}