Make sure NotSelector selects series with label not set

Fixes prometheus#3575

Comes with a slight performance penalty which is better off
addressed in tsdb

Signed-off-by: Goutham Veeramachaneni <gouthamve@gmail.com>

storage/fanout.go

@@ -225,7 +225,7 @@ func (q *mergeQuerier) Select(matchers ...*labels.Matcher) (SeriesSet, error) {
 		}
 		seriesSets = append(seriesSets, set)
 	}
-	return NewMergeSeriesSet(seriesSets), nil
+	return NewMergeSeriesSet(seriesSets...), nil
 }
 
 // LabelValues returns all potential values for a label name.
@@ -302,7 +302,7 @@ type mergeSeriesSet struct {
 
 // NewMergeSeriesSet returns a new series set that merges (deduplicates)
 // series returned by the input series sets when iterating.
-func NewMergeSeriesSet(sets []SeriesSet) SeriesSet {
+func NewMergeSeriesSet(sets ...SeriesSet) SeriesSet {
 	// Sets need to be pre-advanced, so we can introspect the label of the
 	// series under the cursor.
 	var h seriesSetHeap

storage/fanout_test.go

@@ -97,7 +97,7 @@ func TestMergeSeriesSet(t *testing.T) {
 			),
 		},
 	} {
-		merged := NewMergeSeriesSet(tc.input)
+		merged := NewMergeSeriesSet(tc.input...)
 		for merged.Next() {
 			require.True(t, tc.expected.Next())
 			actualSeries := merged.At()

storage/tsdb/tsdb.go

@@ -190,14 +190,39 @@ type querier struct {
 
 func (q querier) Select(oms ...*labels.Matcher) (storage.SeriesSet, error) {
 	ms := make([]tsdbLabels.Matcher, 0, len(oms))
+	var err error
+	notSeen := false
 
-	for _, om := range oms {
+	for i, om := range oms {
 		ms = append(ms, convertMatcher(om))
+
+		// See: https://github.com/prometheus/prometheus/issues/3575
+		if om.Type == labels.MatchNotRegexp || om.Type == labels.MatchNotEqual {
+			if notSeen == false {
+				notSeen = true
+
+				oms[i], err = labels.NewMatcher(labels.MatchEqual, om.Name, "")
+				if err != nil {
+					return nil, err
+				}
+			}
+		}
 	}
+
 	set, err := q.q.Select(ms...)
 	if err != nil {
 		return nil, err
 	}
+
+	if notSeen {
+		lMissingSet, err := q.Select(oms...)
+		if err != nil {
+			return nil, err
+		}
+
+		return storage.NewMergeSeriesSet(lMissingSet, seriesSet{set: set}), nil
+	}
+
 	return seriesSet{set: set}, nil
 }
 

web/api/v1/api.go

@@ -403,7 +403,7 @@ func (api *API) series(r *http.Request) (interface{}, *apiError) {
 		sets = append(sets, s)
 	}
 
-	set := storage.NewMergeSeriesSet(sets)
+	set := storage.NewMergeSeriesSet(sets...)
 	metrics := []labels.Labels{}
 	for set.Next() {
 		metrics = append(metrics, set.At().Labels())

web/federate.go

@@ -83,7 +83,7 @@ func (h *Handler) federation(w http.ResponseWriter, req *http.Request) {
 		sets = append(sets, s)
 	}
 
-	set := storage.NewMergeSeriesSet(sets)
+	set := storage.NewMergeSeriesSet(sets...)
 	for set.Next() {
 		s := set.At()