ddl: fix a bug when adding an index to a generated column with an exp…

…ression error (#9216)

ddl/db_test.go

@@ -2340,3 +2340,25 @@ func (s *testDBSuite) TestAddColumn2(c *C) {
 	re.Check(testkit.Rows("1 2"))
 	s.tk.MustQuery("select a,b,_tidb_rowid from t2").Check(testkit.Rows("1 3 2"))
 }
+
+func (s *testDBSuite) TestAddIndexForGeneratedColumn(c *C) {
+	s.tk = testkit.NewTestKit(c, s.store)
+	s.tk.MustExec("use test_db")
+	s.tk.MustExec("create table t(y year NOT NULL DEFAULT '2155')")
+	defer s.mustExec(c, "drop table t;")
+	for i := 0; i < 50; i++ {
+		s.mustExec(c, "insert into t values (?)", i)
+	}
+	s.tk.MustExec("insert into t values()")
+	s.tk.MustExec("ALTER TABLE t ADD COLUMN y1 year as (y + 2)")
+	_, err := s.tk.Exec("ALTER TABLE t ADD INDEX idx_y(y1)")
+	c.Assert(err.Error(), Equals, "[ddl:15]cannot decode index value, because cannot convert datum from unsigned bigint to type year.")
+
+	t := s.testGetTable(c, "t")
+	for _, idx := range t.Indices() {
+		c.Assert(strings.EqualFold(idx.Meta().Name.L, "idx_c2"), IsFalse)
+	}
+	s.mustExec(c, "delete from t where y = 2155")
+	s.mustExec(c, "alter table t add index idx_y(y1)")
+	s.mustExec(c, "alter table t drop index idx_y")
+}

ddl/ddl.go

@@ -76,6 +76,7 @@ var (
 	errInvalidWorker = terror.ClassDDL.New(codeInvalidWorker, "invalid worker")
 	// errNotOwner means we are not owner and can't handle DDL jobs.
 	errNotOwner              = terror.ClassDDL.New(codeNotOwner, "not Owner")
+	errCantDecodeIndex       = terror.ClassDDL.New(codeCantDecodeIndex, "cannot decode index value, because %s")
 	errInvalidDDLJob         = terror.ClassDDL.New(codeInvalidDDLJob, "invalid DDL job")
 	errCancelledDDLJob       = terror.ClassDDL.New(codeCancelledDDLJob, "cancelled DDL job")
 	errInvalidJobFlag        = terror.ClassDDL.New(codeInvalidJobFlag, "invalid job flag")
@@ -617,6 +618,7 @@ const (
 	codeCancelledDDLJob                      = 12
 	codeInvalidRanges                        = 13
 	codeReorgWorkerPanic                     = 14
+	codeCantDecodeIndex                      = 15
 
 	codeInvalidDBState         = 100
 	codeInvalidTableState      = 101

ddl/index.go

@@ -318,7 +318,7 @@ func (w *worker) onCreateIndex(d *ddlCtx, t *meta.Meta, job *model.Job) (ver int
 				// if timeout, we should return, check for the owner and re-wait job done.
 				return ver, nil
 			}
-			if kv.ErrKeyExists.Equal(err) || errCancelledDDLJob.Equal(err) {
+			if kv.ErrKeyExists.Equal(err) || errCancelledDDLJob.Equal(err) || errCantDecodeIndex.Equal(err) {
 				log.Warnf("[ddl] run DDL job %v err %v, convert job to rollback job", job, err)
 				ver, err = convertAddIdxJob2RollbackJob(t, job, tblInfo, indexInfo, err)
 			}
@@ -549,7 +549,7 @@ func (w *addIndexWorker) getIndexRecord(handle int64, recordKey []byte, rawRecor
 	sysZone := timeutil.SystemLocation()
 	_, err := w.rowDecoder.DecodeAndEvalRowWithMap(w.sessCtx, rawRecord, time.UTC, sysZone, w.rowMap)
 	if err != nil {
-		return nil, errors.Trace(err)
+		return nil, errors.Trace(errCantDecodeIndex.GenWithStackByArgs(err))
 	}
 	idxVal := make([]types.Datum, len(idxInfo.Columns))
 	for j, v := range idxInfo.Columns {