ddl: fix issue 2293 (#2316)

ddl/column.go

@@ -307,6 +307,7 @@ func (d *ddl) addTableColumn(t table.Table, columnInfo *model.ColumnInfo, reorgI
 		colMeta.defaultVal, _, err = table.GetColDefaultValue(ctx, columnInfo)
 		if err != nil {
 			job.State = model.JobCancelled
+			log.Errorf("[ddl] fatal: this case shouldn't happen, err:%v", err)
 			return errors.Trace(err)
 		}
 	} else if mysql.HasNotNullFlag(columnInfo.Flag) {

ddl/ddl.go

@@ -1021,6 +1021,15 @@ func (d *ddl) AddColumn(ctx context.Context, ti ast.Ident, spec *ast.AlterTableS
 		return errors.Trace(err)
 	}
 
+	// Check column default value.
+	colInfo := col.ToInfo()
+	if colInfo.DefaultValue != nil {
+		_, _, err := table.GetColDefaultValue(ctx, colInfo)
+		if err != nil {
+			return errors.Trace(err)
+		}
+	}
+
 	job := &model.Job{
 		SchemaID:   schema.ID,
 		TableID:    t.Meta().ID,

ddl/ddl_db_test.go

@@ -505,6 +505,8 @@ func (s *testDBSuite) TestIssue2293(c *C) {
 	s.tk.MustExec("create table t_issue_2293 (a int)")
 	_, err := s.tk.Exec("alter table t add b int not null default ''")
 	c.Assert(err, NotNil)
+	s.tk.MustExec("insert into t_issue_2293 value(1)")
+	s.tk.MustQuery("select * from t_issue_2293").Check(testkit.Rows("1"))
 }
 
 func (s *testDBSuite) TestColumn(c *C) {