Prevent panicking when index segment info not exists (#21664)

Signed-off-by: NCongqi Xia <congqi.xia@zilliz.com>

internal/datacoord/index_meta_test.go

@@ -1234,3 +1234,21 @@ func TestMeta_GetHasUnindexTaskSegments(t *testing.T) {
 		assert.Equal(t, segID, segments[0].ID)
 	})
 }
+
+// see also: https://github.com/milvus-io/milvus/issues/21660
+func TestUpdateSegmentIndexNotExists(t *testing.T) {
+	m := &meta{
+		segments: &SegmentsInfo{
+			segments: map[UniqueID]*SegmentInfo{},
+		},
+		indexes:              map[UniqueID]map[UniqueID]*model.Index{},
+		buildID2SegmentIndex: make(map[UniqueID]*model.SegmentIndex),
+	}
+
+	assert.NotPanics(t, func() {
+		m.updateSegmentIndex(&model.SegmentIndex{
+			SegmentID: 1,
+			IndexID:   2,
+		})
+	})
+}

internal/datacoord/segment_info.go

@@ -19,7 +19,9 @@ package datacoord
 import (
 	"time"
 
+	"github.com/milvus-io/milvus/internal/log"
 	"github.com/milvus-io/milvus/internal/metastore/model"
+	"go.uber.org/zap"
 
 	"github.com/golang/protobuf/proto"
 	"github.com/milvus-io/milvus-proto/go-api/commonpb"
@@ -99,10 +101,18 @@ func (s *SegmentsInfo) SetSegment(segmentID UniqueID, segment *SegmentInfo) {
 
 // SetSegmentIndex sets SegmentIndex with segmentID, perform overwrite if already exists
 func (s *SegmentsInfo) SetSegmentIndex(segmentID UniqueID, segIndex *model.SegmentIndex) {
-	if s.segments[segmentID].segmentIndexes == nil {
-		s.segments[segmentID].segmentIndexes = make(map[UniqueID]*model.SegmentIndex)
+	segment, ok := s.segments[segmentID]
+	if !ok {
+		log.Warn("segment missing for set segment index",
+			zap.Int64("segmentID", segmentID),
+			zap.Int64("indexID", segIndex.IndexID),
+		)
+		return
+	}
+	if segment.segmentIndexes == nil {
+		segment.segmentIndexes = make(map[UniqueID]*model.SegmentIndex)
 	}
-	s.segments[segmentID].segmentIndexes[segIndex.IndexID] = segIndex
+	segment.segmentIndexes[segIndex.IndexID] = segIndex
 }
 
 func (s *SegmentsInfo) DropSegmentIndex(segmentID UniqueID, indexID UniqueID) {