ddl, types: convert the binary default value to proper encoding

ddl/ddl_api.go

@@ -902,13 +902,20 @@ func getDefaultValue(ctx sessionctx.Context, col *table.Column, c *ast.ColumnOpt
 	}
 
 	if v.Kind() == types.KindBinaryLiteral || v.Kind() == types.KindMysqlBit {
-		if tp == mysql.TypeBit ||
-			tp == mysql.TypeString || tp == mysql.TypeVarchar || tp == mysql.TypeVarString ||
-			tp == mysql.TypeBlob || tp == mysql.TypeLongBlob || tp == mysql.TypeMediumBlob || tp == mysql.TypeTinyBlob ||
-			tp == mysql.TypeJSON || tp == mysql.TypeEnum || tp == mysql.TypeSet {
-			// For BinaryLiteral / string fields, when getting default value we cast the value into BinaryLiteral{}, thus we return
-			// its raw string content here.
-			return v.GetBinaryLiteral().ToString(), false, nil
+		if types.IsTypeBlob(tp) || tp == mysql.TypeJSON {
+			// BLOB/TEXT/JSON column cannot have a default value.
+			// Skip the unnecessary decode procedure.
+			return v.GetString(), false, err
+		}
+		if tp == mysql.TypeBit || tp == mysql.TypeString || tp == mysql.TypeVarchar ||
+			tp == mysql.TypeVarString || tp == mysql.TypeEnum || tp == mysql.TypeSet {
+			// For BinaryLiteral or bit fields, we decode the default value to utf8 string.
+			str, err := v.GetBinaryStringDecoded(nil, col.Charset)
+			if err != nil {
+				// Overwrite the decoding error with invalid default value error.
+				err = ErrInvalidDefaultValue.GenWithStackByArgs(col.Name.O)
+			}
+			return str, false, err
 		}
 		// For other kind of fields (e.g. INT), we supply its integer as string value.
 		value, err := v.GetBinaryLiteral().ToInt(ctx.GetSessionVars().StmtCtx)
@@ -3937,7 +3944,7 @@ func setDefaultValue(ctx sessionctx.Context, col *table.Column, option *ast.Colu
 	hasDefaultValue := false
 	value, isSeqExpr, err := getDefaultValue(ctx, col, option)
 	if err != nil {
-		return hasDefaultValue, errors.Trace(err)
+		return false, errors.Trace(err)
 	}
 	if isSeqExpr {
 		if err := checkSequenceDefaultValue(col); err != nil {

ddl/integration_test.go

@@ -0,0 +1,61 @@
+// Copyright 2021 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ddl_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/pingcap/tidb/testkit"
+	"github.com/pingcap/tidb/util/collate"
+)
+
+func TestDefaultValueIsBinaryString(t *testing.T) {
+	collate.SetCharsetFeatEnabledForTest(true)
+	defer collate.SetCharsetFeatEnabledForTest(false)
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tests := []struct {
+		colTp  string
+		defVal string
+		result string
+	}{
+		{"char(10) charset gbk", "0xC4E3BAC3", "你好"},
+		{"char(10) charset gbk", "'好'", "好"},
+		{"varchar(10) charset gbk", "0xC4E3BAC3", "你好"},
+		{"char(10) charset utf8mb4", "0xE4BDA0E5A5BD", "你好"},
+		{"char(10) charset utf8mb4", "0b111001001011100010010110111001111001010110001100", "世界"},
+		{"bit(48)", "0xE4BDA0E5A5BD", "你好"},
+		{"enum('你好')", "0xE4BDA0E5A5BD", "你好"},
+		{"set('你好')", "0xE4BDA0E5A5BD", "你好"},
+	}
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test;")
+	for _, tt := range tests {
+		tk.MustExec("drop table if exists t;")
+		template := "create table t (a %s default %s);"
+		tk.MustExec(fmt.Sprintf(template, tt.colTp, tt.defVal))
+		tk.MustExec("insert into t values (default);")
+		tk.MustQuery("select a from t;").Check(testkit.Rows(tt.result))
+	}
+
+	// Test invalid default value.
+	tk.MustExec("drop table if exists t;")
+	// 0xE4BDA0E5A5BD81 is an invalid utf-8 string.
+	tk.MustGetErrMsg("create table t (a char(20) charset utf8mb4 default 0xE4BDA0E5A5BD81);",
+		"[ddl:1067]Invalid default value for 'a'")
+	tk.MustGetErrMsg("create table t (a blob default 0xE4BDA0E5A5BD81);",
+		"[ddl:1101]BLOB/TEXT/JSON column 'a' can't have a default value")
+}

types/datum.go

@@ -222,6 +222,9 @@ func (d *Datum) GetStringWithCheck(sc *stmtctx.StatementContext, chs string) (st
 
 func findEncoding(sc *stmtctx.StatementContext, chs string) (enc charset.Encoding, skip bool) {
 	enc = charset.FindEncoding(chs)
+	if sc == nil {
+		return enc, false
+	}
 	if enc.Tp() == charset.EncodingTpUTF8 && sc.SkipUTF8Check ||
 		enc.Tp() == charset.EncodingTpASCII && sc.SkipASCIICheck {
 		return nil, true