fix: filter deleted indexes in GetIndexedSegments to prevent stale segment loading

GetIndexedSegments included deleted index entries in targetIndices but
skipped them in the counting loop, causing indexedFields to never equal
len(targetIndices) when deleted entries existed. This made every segment
appear unindexed after drop+create index cycles, forcing
GetQueryVChanPositions to fall back to loading stale pre-compaction
segments instead of the optimized one.

pr: milvus-io#48558
See also: milvus-io#48557

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

Author: XuanYang-cn

internal/datacoord/index_meta.go

@@ -562,7 +562,7 @@ func (m *indexMeta) GetIndexedSegments(collectionID int64, segmentIDs, fieldIDs
 	matchedFields := typeutil.NewUniqueSet()
 
 	targetIndices := lo.Filter(lo.Values(fieldIndexes), func(index *model.Index, _ int) bool {
-		return fieldIDSet.Contain(index.FieldID)
+		return fieldIDSet.Contain(index.FieldID) && !index.IsDeleted
 	})
 	for _, index := range targetIndices {
 		matchedFields.Insert(index.FieldID)
@@ -576,10 +576,6 @@ func (m *indexMeta) GetIndexedSegments(collectionID int64, segmentIDs, fieldIDs
 	checkSegmentState := func(indexes *typeutil.ConcurrentMap[UniqueID, *model.SegmentIndex]) bool {
 		indexedFields := 0
 		for _, index := range targetIndices {
-			if !fieldIDSet.Contain(index.FieldID) || index.IsDeleted {
-				continue
-			}
-
 			if segIdx, ok := indexes.Get(index.IndexID); ok && segIdx.IndexState == commonpb.IndexState_Finished {
 				indexedFields += 1
 			}

internal/datacoord/index_meta_test.go

@@ -816,6 +816,35 @@ func TestMeta_GetIndexedSegment(t *testing.T) {
 		segments := m.GetIndexedSegments(collID+1, []int64{segID}, []int64{fieldID})
 		assert.Len(t, segments, 0)
 	})
+
+	t.Run("with deleted index entries", func(t *testing.T) {
+		// Simulate drop+create index cycles: add deleted index entries for the same field.
+		// Previously, deleted entries inflated len(targetIndices), causing the indexed check
+		// to always fail (indexedFields=1 != len(targetIndices)=N).
+		deletedIndexID1 := indexID + 100
+		deletedIndexID2 := indexID + 200
+		m.indexes[collID][deletedIndexID1] = &model.Index{
+			CollectionID: collID,
+			FieldID:      fieldID,
+			IndexID:      deletedIndexID1,
+			IndexName:    "old_idx_1",
+			IsDeleted:    true,
+		}
+		m.indexes[collID][deletedIndexID2] = &model.Index{
+			CollectionID: collID,
+			FieldID:      fieldID,
+			IndexID:      deletedIndexID2,
+			IndexName:    "old_idx_2",
+			IsDeleted:    true,
+		}
+
+		segments := m.GetIndexedSegments(collID, []int64{segID}, []int64{fieldID})
+		assert.Len(t, segments, 1, "segment should be indexed even with deleted index entries")
+
+		// Cleanup
+		delete(m.indexes[collID], deletedIndexID1)
+		delete(m.indexes[collID], deletedIndexID2)
+	})
 }
 
 func TestMeta_MarkIndexAsDeleted(t *testing.T) {