Supporting having both nhcb and classic in converter layer

Signed-off-by: Raphael Bizos <r.bizos@criteo.com>

storage/nhcb_querier.go

@@ -81,8 +81,9 @@ func (q *NHCBAsClassicQuerier) Select(ctx context.Context, sortSeries bool, hint
 		return ErrSeriesSet(err)
 	}
 
+	seriesSets := make([]SeriesSet, 0, 2)
 	if len(classicSeries) > 0 {
-		return &bufferedSeriesSet{series: classicSeries}
+		seriesSets = append(seriesSets, &bufferedSeriesSet{series: classicSeries})
 	}
 
 	baseMatchers = append(baseMatchers, labels.MustNewMatcher(labels.MatchEqual, model.MetricNameLabel, metricName))
@@ -90,11 +91,15 @@ func (q *NHCBAsClassicQuerier) Select(ctx context.Context, sortSeries bool, hint
 	if nhcbSet.Err() != nil {
 		return nhcbSet
 	}
-
-	return &nhcbToClassicSeriesSet{
+	seriesSets = append(seriesSets, &nhcbToClassicSeriesSet{
 		nhcbSet:    nhcbSet,
 		suffix:     suffix,
 		metricName: metricName,
+	})
+
+	return &multipleSeriesSet{
+		seriesSet: seriesSets,
+		idx:       0,
 	}
 }
 
@@ -162,6 +167,43 @@ func extractHistogramSuffix(matchers []*labels.Matcher) (string, string, []*labe
 	return baseName, suffix, baseMatchers
 }
 
+type multipleSeriesSet struct {
+	seriesSet []SeriesSet
+	idx       int
+}
+
+func (m *multipleSeriesSet) Next() bool {
+	if m.idx >= len(m.seriesSet) {
+		return false
+	}
+	if !(m.seriesSet[m.idx].Next()) {
+		m.idx++
+		return m.Next()
+	}
+	return true
+}
+
+func (m *multipleSeriesSet) At() Series {
+	return m.seriesSet[m.idx].At()
+}
+
+func (m *multipleSeriesSet) Err() error {
+	for _, ss := range m.seriesSet {
+		if err := ss.Err(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (m *multipleSeriesSet) Warnings() annotations.Annotations {
+	var w annotations.Annotations
+	for _, ss := range m.seriesSet {
+		w.Merge(ss.Warnings())
+	}
+	return w
+}
+
 // nhcbToClassicSeriesSet converts NHCB series to classic histogram series format.
 type nhcbToClassicSeriesSet struct {
 	nhcbSet    SeriesSet

storage/nhcb_querier_test.go

@@ -140,6 +140,18 @@ func TestNHCBAsClassicQuerier_Select(t *testing.T) {
 			expectedCount:  1,
 			expectedSuffix: "_sum",
 		},
+		{
+			name:          "both classic and NHCB - return both",
+			queryMatchers: []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, model.MetricNameLabel, "http_requests_bucket")},
+			classicSeries: []Series{
+				NewListSeries(labels.FromStrings("__name__", "http_requests_bucket", "le", "1"), []chunks.Sample{fSample{t: 1, f: 5}}),
+			},
+			nhcbSeries: []Series{
+				NewListSeries(labels.FromStrings("__name__", "http_requests"), []chunks.Sample{hSample{t: 1, h: nhcb}}),
+			},
+			expectedCount:  5,
+			expectedSuffix: "_bucket",
+		},
 		{
 			name:          "no classic and no NHCB - return empty",
 			queryMatchers: []*labels.Matcher{labels.MustNewMatcher(labels.MatchEqual, model.MetricNameLabel, "http_requests_bucket")},