Add prefix label matcher.

Implement labels.PrefixMatcher and use interface conversion in querier
to optimize label tuples search.

[unit-tests]: Fix bug and populate label index for mock index.

Signed-off-by: Dmitry Ilyevsky <ilyevsky@gmail.com>

labels/selector.go

@@ -13,7 +13,10 @@
 
 package labels
 
-import "regexp"
+import (
+	"regexp"
+	"strings"
+)
 
 // Selector holds constraints for matching against a label set.
 type Selector []Matcher
@@ -84,3 +87,22 @@ func (m *notMatcher) Matches(v string) bool { return !m.Matcher.Matches(v) }
 func Not(m Matcher) Matcher {
 	return &notMatcher{m}
 }
+
+// PrefixMatcher implements Matcher for labels which values matches prefix.
+type PrefixMatcher struct {
+	name, prefix string
+}
+
+// NewPrefixMatcher returns new Matcher for label name matching prefix.
+func NewPrefixMatcher(name, prefix string) Matcher {
+	return &PrefixMatcher{name: name, prefix: prefix}
+}
+
+// Name implements Matcher interface.
+func (m *PrefixMatcher) Name() string { return m.name }
+
+// Prefix returns matching prefix.
+func (m *PrefixMatcher) Prefix() string { return m.prefix }
+
+// Matches implements Matcher interface.
+func (m *PrefixMatcher) Matches(v string) bool { return strings.HasPrefix(v, m.prefix) }

querier.go

@@ -15,6 +15,7 @@ package tsdb
 
 import (
 	"fmt"
+        "sort"
 	"strings"
 
 	"github.com/prometheus/tsdb/chunks"
@@ -220,6 +221,37 @@ func (r *postingsReader) Select(ms ...labels.Matcher) (Postings, []string) {
 	return p, absent
 }
 
+// tuplesByPrefix uses binary search to find prefix matches within ts.
+func tuplesByPrefix(m *labels.PrefixMatcher, ts StringTuples) ([]string, error) {
+	var outErr error
+	tslen := ts.Len()
+	i := sort.Search(tslen, func(i int) bool {
+		vs, err := ts.At(i)
+		if err != nil {
+			outErr = fmt.Errorf("Failed to read tuple %d/%d: %v", i, tslen, err)
+			return true
+		}
+		val := vs[0]
+		l := len(m.Prefix())
+		if l > len(vs) {
+			l = len(val)
+		}
+		return val[:l] >= m.Prefix()
+	})
+	if outErr != nil {
+		return nil, outErr
+	}
+	var matches []string
+	for ; i < tslen; i++ {
+		vs, err := ts.At(i)
+		if err != nil || !m.Matches(vs[0]) {
+			return matches, err
+		}
+		matches = append(matches, vs[0])
+	}
+	return matches, nil
+}
+
 func (r *postingsReader) selectSingle(m labels.Matcher) Postings {
 	// Fast-path for equal matching.
 	if em, ok := m.(*labels.EqualMatcher); ok {
@@ -230,15 +262,19 @@ func (r *postingsReader) selectSingle(m labels.Matcher) Postings {
 		return it
 	}
 
-	// TODO(fabxc): use interface upgrading to provide fast solution
-	// for prefix matches. Tuples are lexicographically sorted.
 	tpls, err := r.index.LabelValues(m.Name())
 	if err != nil {
 		return errPostings{err: err}
 	}
 
 	var res []string
+	if pm, ok := m.(*labels.PrefixMatcher); ok {
+		res, err = tuplesByPrefix(pm, tpls)
+		if err != nil {
+			return errPostings{err: err}
+		}
 
+	} else {
 		for i := 0; i < tpls.Len(); i++ {
 			vals, err := tpls.At(i)
 			if err != nil {
@@ -248,6 +284,7 @@ func (r *postingsReader) selectSingle(m labels.Matcher) Postings {
 				res = append(res, vals[0])
 			}
 		}
+	}
 
 	if len(res) == 0 {
 		return emptyPostings

querier_test.go

@@ -230,6 +230,7 @@ func createIdxChkReaders(tc []struct {
 
 	postings := &memPostings{m: make(map[term][]uint32, 512)}
 	chkReader := mockChunkReader(make(map[uint64]chunks.Chunk))
+	lblIdx := make(map[string]stringset)
 	mi := newMockIndex()
 
 	for i, s := range tc {
@@ -253,16 +254,28 @@ func createIdxChkReaders(tc []struct {
 			chkReader[ref] = chunk
 		}
 
-		mi.AddSeries(uint32(i), labels.FromMap(s.lset), metas...)
+		ls := labels.FromMap(s.lset)
+		mi.AddSeries(uint32(i), ls, metas...)
 
 		postings.add(uint32(i), term{})
-		for _, l := range labels.FromMap(s.lset) {
+		for _, l := range ls {
 			postings.add(uint32(i), term{l.Name, l.Value})
+
+			vs, present := lblIdx[l.Name]
+			if !present {
+				vs = stringset{}
+				lblIdx[l.Name] = vs
 			}
+			vs.set(l.Value)
+		}
+	}
+
+	for l, vs := range lblIdx {
+		mi.WriteLabelIndex([]string{l}, vs.slice())
 	}
 
 	for tm := range postings.m {
-		mi.WritePostings(tm.name, tm.name, postings.get(tm))
+		mi.WritePostings(tm.name, tm.value, postings.get(tm))
 	}
 
 	return mi, chkReader
@@ -334,6 +347,47 @@ func TestBlockQuerier(t *testing.T) {
 					},
 				},
 			},
+			{
+				lset: map[string]string{
+					"p": "abcd",
+					"x": "xyz",
+				},
+				chunks: [][]sample{
+					{
+						{1, 2}, {2, 3}, {3, 4},
+					},
+					{
+						{5, 2}, {6, 3}, {7, 4},
+					},
+				},
+			},
+			{
+				lset: map[string]string{
+					"a": "ab",
+					"p": "abce",
+				},
+				chunks: [][]sample{
+					{
+						{1, 1}, {2, 2}, {3, 3},
+					},
+					{
+						{5, 3}, {6, 6},
+					},
+				},
+			},
+			{
+				lset: map[string]string{
+					"p": "xyz",
+				},
+				chunks: [][]sample{
+					{
+						{1, 1}, {2, 2}, {3, 3},
+					},
+					{
+						{4, 4}, {5, 5}, {6, 6},
+					},
+				},
+			},
 		},
 
 		queries: []query{
@@ -373,11 +427,30 @@ func TestBlockQuerier(t *testing.T) {
 					),
 				}),
 			},
+			{
+				mint: 2,
+				maxt: 6,
+				ms:   []labels.Matcher{labels.NewPrefixMatcher("p", "abc")},
+				exp: newListSeriesSet([]Series{
+					newSeries(map[string]string{
+						"p": "abcd",
+						"x": "xyz",
+					},
+						[]sample{{2, 3}, {3, 4}, {5, 2}, {6, 3}},
+					),
+					newSeries(map[string]string{
+						"a": "ab",
+						"p": "abce",
+					},
+						[]sample{{2, 2}, {3, 3}, {5, 3}, {6, 6}},
+					),
+				}),
+			},
 		},
 	}
 
 Outer:
-	for _, c := range cases.queries {
+	for i, c := range cases.queries {
 		ir, cr := createIdxChkReaders(cases.data)
 		querier := &blockQuerier{
 			index:      ir,
@@ -392,7 +465,7 @@ Outer:
 
 		for {
 			eok, rok := c.exp.Next(), res.Next()
-			require.Equal(t, eok, rok, "next")
+			require.Equal(t, eok, rok, "%d: next", i)
 
 			if !eok {
 				continue Outer
@@ -400,13 +473,13 @@ Outer:
 			sexp := c.exp.At()
 			sres := res.At()
 
-			require.Equal(t, sexp.Labels(), sres.Labels(), "labels")
+			require.Equal(t, sexp.Labels(), sres.Labels(), "%d: labels", i)
 
 			smplExp, errExp := expandSeriesIterator(sexp.Iterator())
 			smplRes, errRes := expandSeriesIterator(sres.Iterator())
 
-			require.Equal(t, errExp, errRes, "samples error")
+			require.Equal(t, errExp, errRes, "%d: samples error", i)
-			require.Equal(t, smplExp, smplRes, "samples")
+			require.Equal(t, smplExp, smplRes, "%d: samples", i)
 		}
 	}