ddl: fix check column field length when add column (#9143)

ddl/db_test.go

@@ -2189,7 +2189,8 @@ func (s *testDBSuite) TestCheckTooBigFieldLength(c *C) {
 	s.tk.MustExec("create table tr_03 (id int, name varchar(65534), purchased date ) default charset=latin1;")
 
 	s.tk.MustExec("drop table if exists tr_04;")
-	s.tk.MustExec("create table tr_04 (a varchar(20000)) default charset utf8;")
+	s.tk.MustExec("create table tr_04 (a varchar(20000) ) default charset utf8;")
+	assertErrorCode(c, s.tk, "alter table tr_04 add column b varchar(20000) charset utf8mb4;", tmysql.ErrTooBigFieldlength)
 	assertErrorCode(c, s.tk, "alter table tr_04 convert to character set utf8mb4;", tmysql.ErrTooBigFieldlength)
 	assertErrorCode(c, s.tk, "create table tr (id int, name varchar(30000), purchased date )  default charset=utf8 collate=utf8_bin;", tmysql.ErrTooBigFieldlength)
 	assertErrorCode(c, s.tk, "create table tr (id int, name varchar(20000) charset utf8mb4, purchased date ) default charset=utf8 collate=utf8;", tmysql.ErrTooBigFieldlength)

ddl/ddl_api.go

@@ -471,6 +471,10 @@ func columnDefToCol(ctx sessionctx.Context, offset int, colDef *ast.ColumnDef, o
 	if err != nil {
 		return nil, nil, errors.Trace(err)
 	}
+	err = checkColumnFieldLength(col)
+	if err != nil {
+		return nil, nil, errors.Trace(err)
+	}
 	return col, constraints, nil
 }
 
@@ -725,16 +729,6 @@ func checkColumnsAttributes(colDefs []*ast.ColumnDef) error {
 	return nil
 }
 
-// checkColumnsFieldLength check the maximum length limit for different character set varchar type columns.
-func checkColumnsFieldLength(cols []*table.Column) error {
-	for _, col := range cols {
-		if err := checkColumnFieldLength(col); err != nil {
-			return errors.Trace(err)
-		}
-	}
-	return nil
-}
-
 func checkColumnFieldLength(col *table.Column) error {
 	if col.Tp == mysql.TypeVarchar {
 		if err := IsTooBigFieldLength(col.Flen, col.Name.O, col.Charset); err != nil {
@@ -1036,10 +1030,6 @@ func buildTableInfoWithCheck(ctx sessionctx.Context, d *ddl, s *ast.CreateTableS
 		return nil, errors.Trace(err)
 	}
 
-	if err = checkColumnsFieldLength(cols); err != nil {
-		return nil, errors.Trace(err)
-	}
-
 	err = checkConstraintNames(newConstraints)
 	if err != nil {
 		return nil, errors.Trace(err)