table, executor: set a real enum as the default enum value

executor/write_test.go

@@ -2115,3 +2115,11 @@ func (s *testSuite) TestDeferConstraintCheckForInsert(c *C) {
 	tk.MustExec(`commit;`)
 	tk.MustQuery(`select * from t;`).Check(testkit.Rows("2"))
 }
+
+func (s *testSuite) TestDefEnumInsert(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("create table test (id int, prescription_type enum('a','b','c','d','e','f') NOT NULL, primary key(id));")
+	tk.MustExec("insert into test (id)  values (1)")
+	tk.MustQuery("select prescription_type from test").Check(testkit.Rows("a"))
+}

table/column.go

@@ -358,7 +358,11 @@ func getColDefaultValueFromNil(ctx sessionctx.Context, col *model.ColumnInfo) (t
 	if col.Tp == mysql.TypeEnum {
 		// For enum type, if no default value and not null is set,
 		// the default value is the first element of the enum list
-		return types.NewDatum(col.FieldType.Elems[0]), nil
+		defEnum, err := types.ParseEnumValue(col.FieldType.Elems, 1)
+		if err != nil {
+			return types.Datum{}, err
+		}
+		return types.NewMysqlEnumDatum(defEnum), nil
 	}
 	if mysql.HasAutoIncrementFlag(col.Flag) {
 		// Auto increment column doesn't has default value and we should not return error.

types/datum.go

@@ -1757,6 +1757,12 @@ func NewMysqlBitDatum(b BinaryLiteral) (d Datum) {
 	return d
 }
 
+// NewMysqlEnumDatum creates a new MysqlEnum Datum for a Enum value.
+func NewMysqlEnumDatum(e Enum) (d Datum) {
+	d.SetMysqlEnum(e)
+	return d
+}
+
 // MakeDatums creates datum slice from interfaces.
 func MakeDatums(args ...interface{}) []Datum {
 	datums := make([]Datum, len(args))