Fix DataNode panic when compact empty segment (#15580)

remove the TODO in compactor

See also: #15573

Signed-off-by: yangxuan <xuan.yang@zilliz.com>

internal/datanode/compactor.go

@@ -379,11 +379,22 @@ func (t *compactionTask) compact() error {
 	g, gCtx := errgroup.WithContext(ctxTimeout)
 	for _, s := range t.plan.GetSegmentBinlogs() {
 
-		// TODO may panic
+		// Get the number of field binlog files from non-empty segment
-		fieldNum := len(s.GetFieldBinlogs()[0].GetBinlogs())
+		var binlogNum int
+		for _, b := range s.GetFieldBinlogs() {
+			if b != nil {
+				binlogNum = len(b.GetBinlogs())
+				break
+			}
+		}
+		// Unable to deal with all empty segments cases, so return error
+		if binlogNum == 0 {
+			log.Error("compact wrong, all segments' binlogs are empty", zap.Int64("planID", t.plan.GetPlanID()))
+			return errIllegalCompactionPlan
+		}
 
-		for idx := 0; idx < fieldNum; idx++ {
+		for idx := 0; idx < binlogNum; idx++ {
-			ps := make([]string, 0, fieldNum)
+			var ps []string
 			for _, f := range s.GetFieldBinlogs() {
 				ps = append(ps, f.GetBinlogs()[idx].GetLogPath())
 			}

internal/datanode/compactor_test.go

@@ -435,17 +435,17 @@ func TestCompactorInterfaceMethods(t *testing.T) {
 		cpaths, err := mockbIO.upload(context.TODO(), segID, partID, []*InsertData{iData}, dData, meta)
 		require.NoError(t, err)
 		require.Equal(t, 11, len(cpaths.inPaths))
-
+		segBinlogs := []*datapb.CompactionSegmentBinlogs{
-		plan := &datapb.CompactionPlan{
-			PlanID: 10080,
-			SegmentBinlogs: []*datapb.CompactionSegmentBinlogs{
 			{
 				SegmentID:           segID,
 				FieldBinlogs:        cpaths.inPaths,
 				Field2StatslogPaths: cpaths.statsPaths,
 				Deltalogs:           cpaths.deltaInfo,
-				},
+			}}
-			},
+
+		plan := &datapb.CompactionPlan{
+			PlanID:           10080,
+			SegmentBinlogs:   segBinlogs,
 			StartTime:        0,
 			TimeoutInSeconds: 1,
 			Type:             datapb.CompactionType_InnerCompaction,
@@ -473,6 +473,21 @@ func TestCompactorInterfaceMethods(t *testing.T) {
 		planID := task.getPlanID()
 		assert.Equal(t, plan.GetPlanID(), planID)
 
+		err = mockKv.RemoveWithPrefix("/")
+		require.NoError(t, err)
+		cpaths, err = mockbIO.upload(context.TODO(), segID, partID, []*InsertData{iData}, dData, meta)
+		require.NoError(t, err)
+		plan.PlanID = 999876
+		segmentBinlogsWithEmptySegment := []*datapb.CompactionSegmentBinlogs{
+			{
+				SegmentID: segID,
+			},
+		}
+		plan.SegmentBinlogs = segmentBinlogsWithEmptySegment
+		err = task.compact()
+		assert.Error(t, err)
+
+		plan.SegmentBinlogs = segBinlogs
 		// New test, remove all the binlogs in memkv
 		//  Deltas in timetravel range
 		err = mockKv.RemoveWithPrefix("/")
@@ -500,6 +515,7 @@ func TestCompactorInterfaceMethods(t *testing.T) {
 		mockfm.sleepSeconds = plan.TimeoutInSeconds + int32(1)
 		err = task.compact()
 		assert.Error(t, err)
+
 	})
 
 	t.Run("Test typeII compact valid", func(t *testing.T) {