``GetFingerprintsForLabelSet`` uses intersection.

This implementation needs to be cleaned up considerably, but it
should hopefully provide some breathing room.  Ultimately this will
be extracted out of the storage layer---specifically the LevelDB
hierarchy---to interface with a generic set of abstractions for a
storage system, but this will be where it remains for now.

storage/metric/leveldb/reading.go

@@ -22,6 +22,7 @@ import (
 	"github.com/matttproud/prometheus/model"
 	dto "github.com/matttproud/prometheus/model/generated"
 	"github.com/matttproud/prometheus/storage/metric"
+	"github.com/matttproud/prometheus/utility"
 	"time"
 )
 
@@ -170,7 +171,7 @@ func (l *LevelDBMetricPersistence) GetFingerprintsForLabelSet(labelSet *model.La
 		m.Increment()
 	}()
 
-	fps = make([]*model.Fingerprint, 0, 0)
+	sets := []utility.Set{}
 
 	for _, labelSetDTO := range model.LabelSetToDTOs(labelSet) {
 		f, err := l.labelSetToFingerprints.Get(coding.NewProtocolBufferEncoder(labelSetDTO))
@@ -184,10 +185,29 @@ func (l *LevelDBMetricPersistence) GetFingerprintsForLabelSet(labelSet *model.La
 			return fps, err
 		}
 
+		set := utility.Set{}
+
 		for _, m := range unmarshaled.Member {
 			fp := model.Fingerprint(*m.Signature)
-			fps = append(fps, &fp)
+			set.Add(fp)
 		}
+
+		sets = append(sets, set)
+	}
+
+	numberOfSets := len(sets)
+	if numberOfSets == 0 {
+		return
+	}
+
+	base := sets[0]
+	for i := 1; i < numberOfSets; i++ {
+		base = base.Intersection(sets[i])
+	}
+	fps = []*model.Fingerprint{}
+	for _, e := range base.Elements() {
+		fingerprint := e.(model.Fingerprint)
+		fps = append(fps, &fingerprint)
 	}
 
 	return

storage/metric/leveldb/regressions_test.go

@@ -0,0 +1,76 @@
+// Copyright 2012 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package leveldb
+
+import (
+	"github.com/matttproud/prometheus/model"
+	"io/ioutil"
+	"os"
+	"testing"
+	"time"
+)
+
+func TestGetFingerprintsForLabelSetUsesAnd(t *testing.T) {
+	temporaryDirectory, _ := ioutil.TempDir("", "test_get_fingerprints_for_label_set_uses_and")
+
+	defer func() {
+		err := os.RemoveAll(temporaryDirectory)
+		if err != nil {
+			t.Errorf("could not remove temporary directory: %f", err)
+		}
+	}()
+
+	persistence, _ := NewLevelDBMetricPersistence(temporaryDirectory)
+	defer persistence.Close()
+
+	metrics := []map[string]string{
+		{"name": "request_metrics_latency_equal_tallying_microseconds", "instance": "http://localhost:9090/metrics.json", "percentile": "0.010000"},
+		{"name": "requests_metrics_latency_equal_accumulating_microseconds", "instance": "http://localhost:9090/metrics.json", "percentile": "0.010000"},
+		{"name": "requests_metrics_latency_logarithmic_accumulating_microseconds", "instance": "http://localhost:9090/metrics.json", "percentile": "0.010000"},
+		{"name": "requests_metrics_latency_logarithmic_tallying_microseconds", "instance": "http://localhost:9090/metrics.json", "percentile": "0.010000"},
+		{"name": "targets_healthy_scrape_latency_ms", "instance": "http://localhost:9090/metrics.json", "percentile": "0.010000"},
+	}
+
+	for _, metric := range metrics {
+		m := model.Metric{}
+
+		for k, v := range metric {
+			m[model.LabelName(k)] = model.LabelValue(v)
+		}
+
+		err := persistence.AppendSample(&model.Sample{
+			Value:     model.SampleValue(0.0),
+			Timestamp: time.Now(),
+			Metric:    m,
+		})
+
+		if err != nil {
+			t.Errorf("could not create base sample: %s", err)
+		}
+	}
+
+	labelSet := model.LabelSet{
+		"name":       "targets_healthy_scrape_latency_ms",
+		"percentile": "0.010000",
+	}
+
+	fingerprints, err := persistence.GetFingerprintsForLabelSet(&labelSet)
+	if err != nil {
+		t.Errorf("could not get labels: %s", err)
+	}
+
+	if len(fingerprints) != 1 {
+		t.Errorf("did not get a single metric as is expected, got %s", fingerprints)
+	}
+}