enhance: decrease CPU overhead when calculating index file size (#36579)

issue: #36578

---------

Signed-off-by: jaime <yun.zhang@zilliz.com>

internal/datacoord/index_meta.go

@@ -812,6 +812,25 @@ func (m *indexMeta) GetAllSegIndexes() map[int64]*model.SegmentIndex {
 	return segIndexes
 }
 
+// SetStoredIndexFileSizeMetric returns the total index files size of all segment for each collection.
+func (m *indexMeta) SetStoredIndexFileSizeMetric(collections map[UniqueID]*collectionInfo) uint64 {
+	m.RLock()
+	defer m.RUnlock()
+
+	var total uint64
+	metrics.DataCoordStoredIndexFilesSize.Reset()
+
+	for _, segmentIdx := range m.buildID2SegmentIndex {
+		coll, ok := collections[segmentIdx.CollectionID]
+		if ok {
+			metrics.DataCoordStoredIndexFilesSize.WithLabelValues(coll.DatabaseName,
+				fmt.Sprint(segmentIdx.CollectionID), fmt.Sprint(segmentIdx.SegmentID)).Set(float64(segmentIdx.IndexSize))
+			total += segmentIdx.IndexSize
+		}
+	}
+	return total
+}
+
 func (m *indexMeta) RemoveSegmentIndex(collID, partID, segID, indexID, buildID UniqueID) error {
 	m.Lock()
 	defer m.Unlock()

internal/datacoord/meta.go

@@ -470,18 +470,7 @@ func (m *meta) GetQuotaInfo() *metricsinfo.DataCoordQuotaMetrics {
 func (m *meta) SetStoredIndexFileSizeMetric() uint64 {
 	m.RLock()
 	defer m.RUnlock()
-	var total uint64
+	return m.indexMeta.SetStoredIndexFileSizeMetric(m.collections)
-
-	metrics.DataCoordStoredIndexFilesSize.Reset()
-	for _, segmentIdx := range m.indexMeta.GetAllSegIndexes() {
-		coll, ok := m.collections[segmentIdx.CollectionID]
-		if ok {
-			metrics.DataCoordStoredIndexFilesSize.WithLabelValues(coll.DatabaseName,
-				fmt.Sprint(segmentIdx.CollectionID), fmt.Sprint(segmentIdx.SegmentID)).Set(float64(segmentIdx.IndexSize))
-			total += segmentIdx.IndexSize
-		}
-	}
-	return total
 }
 
 func (m *meta) GetAllCollectionNumRows() map[int64]int64 {