labels: add Compare and String methods

labels/labels.go

 package labels
 
 import (
+	"bytes"
 	"sort"
+	"strconv"
+	"strings"
 
 	"github.com/cespare/xxhash"
 )
@@ -21,6 +24,23 @@ func (ls Labels) Len() int           { return len(ls) }
 func (ls Labels) Swap(i, j int)      { ls[i], ls[j] = ls[j], ls[i] }
 func (ls Labels) Less(i, j int) bool { return ls[i].Name < ls[j].Name }
 
+func (ls Labels) String() string {
+	var b bytes.Buffer
+
+	b.WriteByte('{')
+	for i, l := range ls {
+		if i > 0 {
+			b.WriteByte(',')
+		}
+		b.WriteString(l.Name)
+		b.WriteByte('=')
+		b.WriteString(strconv.Quote(l.Value))
+	}
+	b.WriteByte('}')
+
+	return b.String()
+}
+
 // Hash returns a hash value for the label set.
 func (ls Labels) Hash() uint64 {
 	b := make([]byte, 0, 1024)
@@ -101,3 +121,23 @@ func FromStrings(ss ...string) Labels {
 	sort.Sort(res)
 	return res
 }
+
+// Compare compares the two label sets.
+// The result will be 0 if a==b, <0 if a < b, and >0 if a > b.
+func Compare(a, b Labels) int {
+	l := len(a)
+	if len(b) < l {
+		l = len(b)
+	}
+
+	for i := 0; i < l; i++ {
+		if d := strings.Compare(a[i].Name, b[i].Name); d != 0 {
+			return d
+		}
+		if d := strings.Compare(a[i].Value, b[i].Value); d != 0 {
+			return d
+		}
+	}
+	// If all labels so far were in common, the set with fewer labels comes first.
+	return len(a) - len(b)
+}

querier.go

@@ -340,26 +340,6 @@ func newShardSeriesSet(a, b SeriesSet) *shardSeriesSet {
 	return s
 }
 
-// compareLabels compares the two label sets.
-// The result will be 0 if a==b, <0 if a < b, and >0 if a > b.
-func compareLabels(a, b labels.Labels) int {
-	l := len(a)
-	if len(b) < l {
-		l = len(b)
-	}
-
-	for i := 0; i < l; i++ {
-		if d := strings.Compare(a[i].Name, b[i].Name); d != 0 {
-			return d
-		}
-		if d := strings.Compare(a[i].Value, b[i].Value); d != 0 {
-			return d
-		}
-	}
-	// If all labels so far were in common, the set with fewer labels comes first.
-	return len(a) - len(b)
-}
-
 func (s *shardSeriesSet) Series() Series {
 	return s.cur
 }
@@ -378,7 +358,7 @@ func (s *shardSeriesSet) compare() int {
 	if s.bs == nil {
 		return -1
 	}
-	return compareLabels(s.as.Labels(), s.bs.Labels())
+	return labels.Compare(s.as.Labels(), s.bs.Labels())
 }
 
 func (s *shardSeriesSet) advanceA() {

querier_test.go

@@ -175,58 +175,6 @@ func expandSeriesIterator(it SeriesIterator) (r []sample, err error) {
 	return r, it.Err()
 }
 
-func TestCompareLabels(t *testing.T) {
-	cases := []struct {
-		a, b []labels.Label
-		res  int
-	}{
-		{
-			a:   []labels.Label{},
-			b:   []labels.Label{},
-			res: 0,
-		},
-		{
-			a:   []labels.Label{{"a", ""}},
-			b:   []labels.Label{{"a", ""}, {"b", ""}},
-			res: -1,
-		},
-		{
-			a:   []labels.Label{{"a", ""}},
-			b:   []labels.Label{{"a", ""}},
-			res: 0,
-		},
-		{
-			a:   []labels.Label{{"aa", ""}, {"aa", ""}},
-			b:   []labels.Label{{"aa", ""}, {"ab", ""}},
-			res: -1,
-		},
-		{
-			a:   []labels.Label{{"aa", ""}, {"abb", ""}},
-			b:   []labels.Label{{"aa", ""}, {"ab", ""}},
-			res: 1,
-		},
-		{
-			a: []labels.Label{
-				{"__name__", "go_gc_duration_seconds"},
-				{"job", "prometheus"},
-				{"quantile", "0.75"},
-			},
-			b: []labels.Label{
-				{"__name__", "go_gc_duration_seconds"},
-				{"job", "prometheus"},
-				{"quantile", "1"},
-			},
-			res: -1,
-		},
-	}
-	for _, c := range cases {
-		// Use constructor to ensure sortedness.
-		a, b := labels.New(c.a...), labels.New(c.b...)
-
-		require.Equal(t, c.res, compareLabels(a, b))
-	}
-}
-
 func TestSampleRing(t *testing.T) {
 	cases := []struct {
 		input []int64

writer.go

@@ -325,7 +325,7 @@ func (w *indexWriter) writeSeries() error {
 		series = append(series, s)
 	}
 	slice.Sort(series, func(i, j int) bool {
-		return compareLabels(series[i].labels, series[j].labels) < 0
+		return labels.Compare(series[i].labels, series[j].labels) < 0
 	})
 
 	// Current end of file plus 5 bytes for section header.