Performance optimization suggestions

tsdb/index/inmem/inmem.go

@@ -1066,6 +1066,7 @@ func (i *Index) assignExistingSeries(shardID uint64, seriesIDSet *tsdb.SeriesIDS
 		} else {
 			// Add the existing series to this shard's bitset, since this may
 			// be the first time the series is added to this shard.
+			if !seriesIDSet.Contains(ss.ID) {
 				seriesIDSet.Lock()
 				if !seriesIDSet.ContainsNoLock(ss.ID) {
 					seriesIDSet.AddNoLock(ss.ID)
@@ -1073,6 +1074,7 @@ func (i *Index) assignExistingSeries(shardID uint64, seriesIDSet *tsdb.SeriesIDS
 				seriesIDSet.Unlock()
 			}
 		}
+	}
 	i.mu.RUnlock()
 	return keys[:n], names[:n], tagsSlice[:n]
 }