fix: bm25 search failed when avgdl == nan (#41502)

relate: https://github.com/milvus-io/milvus/issues/41490

---------

Signed-off-by: aoiasd <zhicheng.yue@zilliz.com>

internal/querynodev2/delegator/delegator_data.go

@@ -954,11 +954,6 @@ func (sd *shardDelegator) ReleaseSegments(ctx context.Context, req *querypb.Rele
 			pkoracle.WithSegmentType(commonpb.SegmentState_Sealed),
 			pkoracle.WithWorkerID(targetNodeID),
 		)
-		if sd.idfOracle != nil {
-			for _, segment := range sealed {
-				sd.idfOracle.Remove(segment.SegmentID, commonpb.SegmentState_Sealed)
-			}
-		}
 	}
 	if len(growing) > 0 {
 		sd.pkOracle.Remove(
@@ -967,7 +962,7 @@ func (sd *shardDelegator) ReleaseSegments(ctx context.Context, req *querypb.Rele
 		)
 		if sd.idfOracle != nil {
 			for _, segment := range growing {
-				sd.idfOracle.Remove(segment.SegmentID, commonpb.SegmentState_Growing)
+				sd.idfOracle.RemoveGrowing(segment.SegmentID)
 			}
 		}
 	}
@@ -1126,6 +1121,10 @@ func (sd *shardDelegator) buildBM25IDF(req *internalpb.SearchRequest) (float64,
 		return 0, err
 	}
 
+	if avgdl <= 0 {
+		return 0, nil
+	}
+
 	for _, idf := range idfSparseVector {
 		metrics.QueryNodeSearchFTSNumTokens.WithLabelValues(fmt.Sprint(paramtable.GetNodeID()), fmt.Sprint(sd.collectionID), fmt.Sprint(req.GetFieldId())).Observe(float64(typeutil.SparseFloatRowElementCount(idf)))
 	}

internal/querynodev2/delegator/idf_oracle.go

@@ -40,7 +40,7 @@ type IDFOracle interface {
 	UpdateGrowing(segmentID int64, stats map[int64]*storage.BM25Stats)
 
 	Register(segmentID int64, stats map[int64]*storage.BM25Stats, state commonpb.SegmentState)
-	Remove(segmentID int64, state commonpb.SegmentState)
+	RemoveGrowing(segmentID int64)
 
 	BuildIDF(fieldID int64, tfs *schemapb.SparseFloatArray) ([][]byte, float64, error)
 }
@@ -49,6 +49,7 @@ type bm25Stats struct {
 	stats         map[int64]*storage.BM25Stats
 	activate      bool
 	targetVersion int64
+	snapVersion   int64
 }
 
 func (s *bm25Stats) Merge(stats map[int64]*storage.BM25Stats) {
@@ -133,7 +134,7 @@ func (o *idfOracle) Register(segmentID int64, stats map[int64]*storage.BM25Stats
 		o.sealed[segmentID] = &bm25Stats{
 			stats:         stats,
 			activate:      false,
-			targetVersion: initialTargetVersion,
+			targetVersion: unreadableTargetVersion,
 		}
 	default:
 		log.Warn("register segment with unknown state", zap.String("stats", state.String()))
@@ -160,28 +161,16 @@ func (o *idfOracle) UpdateGrowing(segmentID int64, stats map[int64]*storage.BM25
 	}
 }
 
-func (o *idfOracle) Remove(segmentID int64, state commonpb.SegmentState) {
+func (o *idfOracle) RemoveGrowing(segmentID int64) {
 	o.Lock()
 	defer o.Unlock()
 
-	switch state {
-	case segments.SegmentTypeGrowing:
 	if stats, ok := o.growing[segmentID]; ok {
 		if stats.activate {
 			o.current.Minus(stats.stats)
 		}
 		delete(o.growing, segmentID)
 	}
-	case segments.SegmentTypeSealed:
-		if stats, ok := o.sealed[segmentID]; ok {
-			if stats.activate {
-				o.current.Minus(stats.stats)
-			}
-			delete(o.sealed, segmentID)
-		}
-	default:
-		return
-	}
 }
 
 func (o *idfOracle) activate(stats *bm25Stats) {
@@ -207,7 +196,10 @@ func (o *idfOracle) SyncDistribution(snapshot *snapshot) {
 			}
 
 			if stats, ok := o.sealed[segment.SegmentID]; ok {
+				if stats.targetVersion < segment.TargetVersion {
 					stats.targetVersion = segment.TargetVersion
+				}
+				stats.snapVersion = snapshot.version
 			} else {
 				log.Warn("idf oracle lack some sealed segment", zap.Int64("segmentID", segment.SegmentID))
 			}
@@ -224,11 +216,14 @@ func (o *idfOracle) SyncDistribution(snapshot *snapshot) {
 
 	o.targetVersion = snapshot.targetVersion
 
-	for _, stats := range o.sealed {
+	for segmentID, stats := range o.sealed {
 		if !stats.activate && stats.targetVersion == o.targetVersion {
 			o.activate(stats)
-		} else if stats.activate && stats.targetVersion != o.targetVersion {
-			o.deactivate(stats)
+		} else if (stats.targetVersion < o.targetVersion && stats.targetVersion != unreadableTargetVersion) || stats.snapVersion != snapshot.version {
+			if stats.activate {
+				o.current.Minus(stats.stats)
+			}
+			delete(o.sealed, segmentID)
 		}
 	}
 

internal/querynodev2/delegator/idf_oracle_test.go

@@ -132,10 +132,6 @@ func (suite *IDFOracleSuite) TestSealed() {
 	suite.idfOracle.SyncDistribution(suite.snapshot)
 	suite.Equal(int64(1), suite.idfOracle.current.NumRow())
 
-	for _, segID := range releasedSeg {
-		suite.idfOracle.Remove(segID, commonpb.SegmentState_Sealed)
-	}
-
 	sparse := typeutil.CreateAndSortSparseFloatRow(map[uint32]float32{4: 1})
 	bytes, avgdl, err := suite.idfOracle.BuildIDF(102, &schemapb.SparseFloatArray{Contents: [][]byte{sparse}, Dim: 1})
 	suite.NoError(err)
@@ -165,10 +161,6 @@ func (suite *IDFOracleSuite) TestGrow() {
 
 	suite.idfOracle.UpdateGrowing(4, suite.genStats(5, 6))
 	suite.Equal(int64(2), suite.idfOracle.current.NumRow())
-
-	for _, segID := range releasedSeg {
-		suite.idfOracle.Remove(segID, commonpb.SegmentState_Growing)
-	}
 }
 
 func (suite *IDFOracleSuite) TestStats() {

internal/storage/stats.go

@@ -470,6 +470,9 @@ func (m *BM25Stats) BuildIDF(tf []byte) (idf []byte) {
 }
 
 func (m *BM25Stats) GetAvgdl() float64 {
+	if m.numRow == 0 || m.numToken == 0 {
+		return 0
+	}
 	return float64(m.numToken) / float64(m.numRow)
 }