Merge pull request #13427 from bboreham/skip-empty-merge

storage: skip merging when no remote storage configured

storage/fanout.go

@@ -89,8 +89,10 @@ func (f *fanout) Querier(mint, maxt int64) (Querier, error) {
 			}
 			return nil, errs.Err()
 		}
+		if _, ok := querier.(noopQuerier); !ok {
 			secondaries = append(secondaries, querier)
 		}
+	}
 	return NewMergeQuerier([]Querier{primary}, secondaries, ChainedSeriesMerge), nil
 }
 

storage/merge.go

@@ -46,6 +46,9 @@ type mergeGenericQuerier struct {
 //
 // In case of overlaps between the data given by primaries' and secondaries' Selects, merge function will be used.
 func NewMergeQuerier(primaries, secondaries []Querier, mergeFn VerticalSeriesMergeFunc) Querier {
+	if len(primaries)+len(secondaries) == 0 {
+		return NoopQuerier()
+	}
 	queriers := make([]genericQuerier, 0, len(primaries)+len(secondaries))
 	for _, q := range primaries {
 		if _, ok := q.(noopQuerier); !ok && q != nil {