add-index part

ddl/backfilling_dist_scheduler.go

@@ -106,6 +106,8 @@ type backfillDistScheduler struct {
 	taskTable  scheduler.TaskTable
 	backendCtx ingest.BackendCtx
 	jobID      int64
+
+	uniqueIndex bool
 }
 
 func newBackfillDistScheduler(ctx context.Context, id string, task *proto.Task, taskTable scheduler.TaskTable, d *ddl) scheduler.Scheduler {
@@ -146,6 +148,7 @@ func (s *backfillDistScheduler) Init(ctx context.Context) error {
 	if err != nil {
 		return errors.Trace(err)
 	}
+	s.uniqueIndex = idx.Unique
 	s.backendCtx = bc
 	s.jobID = job.ID
 	return nil
@@ -160,9 +163,10 @@ func (s *backfillDistScheduler) GetSubtaskExecutor(ctx context.Context, task *pr
 	}
 }
 
-func (*backfillDistScheduler) IsIdempotent(*proto.Subtask) bool {
-	// TODO: implement this later.
-	return false
+func (s *backfillDistScheduler) IsIdempotent(*proto.Subtask) bool {
+	// unique index depends on MVCC to do deduplicate, so it's not idempotent.
+	// we might save engine TS later to make it idempotent.
+	return !s.uniqueIndex
 }
 
 func (s *backfillDistScheduler) Close() {

ddl/backfilling_dist_scheduler_test.go

@@ -0,0 +1,31 @@
+// Copyright 2023 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
+
+import (
+	"testing"
+
+	"github.com/pingcap/tidb/disttask/framework/proto"
+	"github.com/stretchr/testify/require"
+)
+
+func TestIsIdempotent(t *testing.T) {
+	s := &backfillDistScheduler{
+		uniqueIndex: false,
+	}
+	require.True(t, s.IsIdempotent(&proto.Subtask{}))
+	s.uniqueIndex = true
+	require.False(t, s.IsIdempotent(&proto.Subtask{}))
+}