enhance: add multiply factor when loading index (#38721)

issue: #38715
pr: #38716

Signed-off-by: chyezh <chyezh@outlook.com>

configs/milvus.yaml

@@ -589,6 +589,8 @@ dataCoord:
       maxClusterSizeRatio: 10 # maximum cluster size / avg size in Kmeans train
       maxClusterSize: 5g # maximum cluster size in Kmeans train
   syncSegmentsInterval: 300 # The time interval for regularly syncing segments
+  index:
+    memSizeEstimateMultiplier: 2 # When the memory size is not setup by index procedure, multiplier to estimate the memory size of index data
   enableGarbageCollection: true # Switch value to control if to enable garbage collection to clear the discarded data in MinIO or S3 service.
   gc:
     interval: 3600 # The interval at which data coord performs garbage collection, unit: second.

internal/querynodev2/segments/segment.go

@@ -1346,7 +1346,8 @@ func GetCLoadInfoWithFunc(ctx context.Context,
 		IndexFiles:         indexInfo.GetIndexFilePaths(),
 		IndexEngineVersion: indexInfo.GetCurrentIndexVersion(),
 		IndexStoreVersion:  indexInfo.GetIndexStoreVersion(),
-		IndexFileSize:      indexInfo.GetIndexSize(),
+		// TODO: For quickly fixing, we add the multiplier here, but those logic should be put at the datacoord after we add the mem size for each index.
+		IndexFileSize: int64(paramtable.Get().DataCoordCfg.IndexMemSizeEstimateMultiplier.GetAsFloat() * float64(indexInfo.GetIndexSize())),
 	}
 
 	// 2.

pkg/util/paramtable/component_param.go

@@ -3273,6 +3273,9 @@ type dataCoordConfig struct {
 	ChannelCheckpointMaxLag ParamItem `refreshable:"true"`
 	SyncSegmentsInterval    ParamItem `refreshable:"false"`
 
+	// Index related configuration
+	IndexMemSizeEstimateMultiplier ParamItem `refreshable:"true"`
+
 	// Clustering Compaction
 	ClusteringCompactionEnable                 ParamItem `refreshable:"true"`
 	ClusteringCompactionAutoEnable             ParamItem `refreshable:"true"`
@@ -3749,6 +3752,15 @@ During compaction, the size of segment # of rows is able to exceed segment max #
 	}
 	p.LevelZeroCompactionTriggerDeltalogMaxNum.Init(base.mgr)
 
+	p.IndexMemSizeEstimateMultiplier = ParamItem{
+		Key:          "dataCoord.index.memSizeEstimateMultiplier",
+		Version:      "2.4.19",
+		DefaultValue: "2",
+		Doc:          "When the memory size is not setup by index procedure, multiplier to estimate the memory size of index data",
+		Export:       true,
+	}
+	p.IndexMemSizeEstimateMultiplier.Init(base.mgr)
+
 	p.ClusteringCompactionEnable = ParamItem{
 		Key:          "dataCoord.compaction.clustering.enable",
 		Version:      "2.4.7",