From b7eeb41c318f3e2dd0cf44faded0bde5d2edd90d Mon Sep 17 00:00:00 2001
From: Hangjie Mo <mohangjie1995@gmail.com>
Date: Mon, 30 May 2022 22:04:26 +0800
Subject: [PATCH] parser: revert `latin1` as an alias for `utf8mb4` (#35025)

ref pingcap/tidb#34008
---
 expression/integration_test.go    |  2 +-
 parser/charset/encoding_latin1.go | 25 ++++++++++++++++++++++++-
 parser/mysql/charset.go           |  4 ++--
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/expression/integration_test.go b/expression/integration_test.go
index 83fa1791e955c..c3734a1a5c184 100644
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -653,7 +653,7 @@ func TestStringBuiltin(t *testing.T) {
 	result = tk.MustQuery("select ord('123'), ord(123), ord(''), ord('你好'), ord(NULL), ord('👍')")
 	result.Check(testkit.Rows("49 49 0 14990752 <nil> 4036989325"))
 	result = tk.MustQuery("select ord(X''), ord(X'6161'), ord(X'e4bd'), ord(X'e4bda0'), ord(_ascii'你'), ord(_latin1'你')")
-	result.Check(testkit.Rows("0 97 228 228 228 14990752"))
+	result.Check(testkit.Rows("0 97 228 228 228 228"))
 
 	// for space
 	result = tk.MustQuery(`select space(0), space(2), space(-1), space(1.1), space(1.9)`)
diff --git a/parser/charset/encoding_latin1.go b/parser/charset/encoding_latin1.go
index f1893484b9a6b..db7b66ed101af 100644
--- a/parser/charset/encoding_latin1.go
+++ b/parser/charset/encoding_latin1.go
@@ -14,11 +14,12 @@
 package charset
 
 import (
+	"bytes"
 	"golang.org/x/text/encoding"
 )
 
 // EncodingLatin1Impl is the instance of encodingLatin1.
-// In TiDB, latin1 is an alias for utf8, so uses utf8 implementation for latin1.
+// TiDB uses utf8 implementation for latin1 charset because of the backward compatibility.
 var EncodingLatin1Impl = &encodingLatin1{encodingUTF8{encodingBase{enc: encoding.Nop}}}
 
 func init() {
@@ -34,3 +35,25 @@ type encodingLatin1 struct {
 func (e *encodingLatin1) Name() string {
 	return CharsetLatin1
 }
+
+// Peek implements Encoding interface.
+func (e *encodingLatin1) Peek(src []byte) []byte {
+	if len(src) == 0 {
+		return src
+	}
+	return src[:1]
+}
+
+// IsValid implements Encoding interface.
+func (e *encodingLatin1) IsValid(src []byte) bool {
+	return true
+}
+
+// Tp implements Encoding interface.
+func (e *encodingLatin1) Tp() EncodingTp {
+	return EncodingTpLatin1
+}
+
+func (e *encodingLatin1) Transform(dest *bytes.Buffer, src []byte, op Op) ([]byte, error) {
+	return src, nil
+}
diff --git a/parser/mysql/charset.go b/parser/mysql/charset.go
index cb3666bb21b31..75ee0563ae5f3 100644
--- a/parser/mysql/charset.go
+++ b/parser/mysql/charset.go
@@ -593,9 +593,9 @@ const (
 	MaxBytesOfCharacter = 4
 )
 
-// IsUTF8Charset checks if charset is utf8, utf8mb4 or latin1.
+// IsUTF8Charset checks if charset is utf8, utf8mb4.
 func IsUTF8Charset(charset string) bool {
-	return charset == UTF8Charset || charset == UTF8MB4Charset || charset == Latin1Charset
+	return charset == UTF8Charset || charset == UTF8MB4Charset
 }
 
 // RangeGraph defines valid unicode characters to use in column names. It strictly follows MySQL's definition.