enhance: change protection to RLock for loadStreamDelete (#29450)

See also: #29332

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

internal/querynodev2/delegator/delegator.go

@@ -101,7 +101,7 @@ type shardDelegator struct {
 	level0Mut       sync.RWMutex
 	level0Deletions map[int64]*storage.DeleteData // partitionID -> deletions
 	// stream delete buffer
-	deleteMut    sync.Mutex
+	deleteMut    sync.RWMutex
 	deleteBuffer deletebuffer.DeleteBuffer[*deletebuffer.Item]
 	// dispatcherClient msgdispatcher.Client
 	factory msgstream.Factory

internal/querynodev2/delegator/delegator_data.go

@@ -570,8 +570,8 @@ func (sd *shardDelegator) loadStreamDelete(ctx context.Context,
 		return candidate.ID(), candidate
 	})
 
-	sd.deleteMut.Lock()
-	defer sd.deleteMut.Unlock()
+	sd.deleteMut.RLock()
+	defer sd.deleteMut.RUnlock()
 	// apply buffered delete for new segments
 	// no goroutines here since qnv2 has no load merging logic
 	for _, info := range infos {