[PERF] TSDB: Optimize inverse matching (#14144)

Simple follow-up to #13620. Modify `tsdb.PostingsForMatchers` to use the optimized tsdb.IndexReader.PostingsForLabelMatching method also for inverse matching.

Introduce method `PostingsForAllLabelValues`, to avoid changing the existing method.

The performance is much improved for a subset of the cases; there are up to
~60% CPU gains and ~12.5% reduction in memory usage. 

Remove `TestReader_InversePostingsForMatcherHonorsContextCancel` since
`inversePostingsForMatcher` only passes `ctx` to `IndexReader` implementations now.

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

tsdb/block.go

@@ -82,6 +82,10 @@ type IndexReader interface {
 	// If no postings are found having at least one matching label, an empty iterator is returned.
 	PostingsForLabelMatching(ctx context.Context, name string, match func(value string) bool) index.Postings
 
+	// PostingsForAllLabelValues returns a sorted iterator over all postings having a label with the given name.
+	// If no postings are found with the label in question, an empty iterator is returned.
+	PostingsForAllLabelValues(ctx context.Context, name string) index.Postings
+
 	// SortedPostings returns a postings list that is reordered to be sorted
 	// by the label set of the underlying series.
 	SortedPostings(index.Postings) index.Postings
@@ -531,6 +535,10 @@ func (r blockIndexReader) PostingsForLabelMatching(ctx context.Context, name str
 	return r.ir.PostingsForLabelMatching(ctx, name, match)
 }
 
+func (r blockIndexReader) PostingsForAllLabelValues(ctx context.Context, name string) index.Postings {
+	return r.ir.PostingsForAllLabelValues(ctx, name)
+}
+
 func (r blockIndexReader) SortedPostings(p index.Postings) index.Postings {
 	return r.ir.SortedPostings(p)
 }

tsdb/head_read.go

@@ -123,6 +123,10 @@ func (h *headIndexReader) PostingsForLabelMatching(ctx context.Context, name str
 	return h.head.postings.PostingsForLabelMatching(ctx, name, match)
 }
 
+func (h *headIndexReader) PostingsForAllLabelValues(ctx context.Context, name string) index.Postings {
+	return h.head.postings.PostingsForAllLabelValues(ctx, name)
+}
+
 func (h *headIndexReader) SortedPostings(p index.Postings) index.Postings {
 	series := make([]*memSeries, 0, 128)
 

tsdb/index/index.go

@@ -1777,6 +1777,15 @@ func (r *Reader) Postings(ctx context.Context, name string, values ...string) (P
 }
 
 func (r *Reader) PostingsForLabelMatching(ctx context.Context, name string, match func(string) bool) Postings {
+	return r.postingsForLabelMatching(ctx, name, match)
+}
+
+func (r *Reader) PostingsForAllLabelValues(ctx context.Context, name string) Postings {
+	return r.postingsForLabelMatching(ctx, name, nil)
+}
+
+// postingsForLabelMatching implements PostingsForLabelMatching if match is non-nil, and PostingsForAllLabelValues otherwise.
+func (r *Reader) postingsForLabelMatching(ctx context.Context, name string, match func(string) bool) Postings {
 	if r.version == FormatV1 {
 		return r.postingsForLabelMatchingV1(ctx, name, match)
 	}
@@ -1786,11 +1795,17 @@ func (r *Reader) PostingsForLabelMatching(ctx context.Context, name string, matc
 		return EmptyPostings()
 	}
 
+	postingsEstimate := 0
+	if match == nil {
+		// The caller wants all postings for name.
+		postingsEstimate = len(e) * symbolFactor
+	}
+
 	lastVal := e[len(e)-1].value
-	var its []Postings
+	its := make([]Postings, 0, postingsEstimate)
 	if err := r.traversePostingOffsets(ctx, e[0].off, func(val string, postingsOff uint64) (bool, error) {
-		if match(val) {
+		if match == nil || match(val) {
-			// We want this postings iterator since the value is a match
+			// We want this postings iterator since the value is a match.
 			postingsDec := encoding.NewDecbufAt(r.b, int(postingsOff), castagnoliTable)
 			_, p, err := r.dec.DecodePostings(postingsDec)
 			if err != nil {
@@ -1819,7 +1834,7 @@ func (r *Reader) postingsForLabelMatchingV1(ctx context.Context, name string, ma
 			return ErrPostings(ctx.Err())
 		}
 		count++
-		if !match(val) {
+		if match != nil && !match(val) {
 			continue
 		}
 

tsdb/index/index_test.go

@@ -613,6 +613,52 @@ func TestChunksTimeOrdering(t *testing.T) {
 	require.NoError(t, idx.Close())
 }
 
+func TestReader_PostingsForLabelMatching(t *testing.T) {
+	const seriesCount = 9
+	var input indexWriterSeriesSlice
+	for i := 1; i <= seriesCount; i++ {
+		input = append(input, &indexWriterSeries{
+			labels: labels.FromStrings("__name__", strconv.Itoa(i)),
+			chunks: []chunks.Meta{
+				{Ref: 1, MinTime: 0, MaxTime: 10},
+			},
+		})
+	}
+	ir, _, _ := createFileReader(context.Background(), t, input)
+
+	p := ir.PostingsForLabelMatching(context.Background(), "__name__", func(v string) bool {
+		iv, err := strconv.Atoi(v)
+		if err != nil {
+			panic(err)
+		}
+		return iv%2 == 0
+	})
+	require.NoError(t, p.Err())
+	refs, err := ExpandPostings(p)
+	require.NoError(t, err)
+	require.Equal(t, []storage.SeriesRef{4, 6, 8, 10}, refs)
+}
+
+func TestReader_PostingsForAllLabelValues(t *testing.T) {
+	const seriesCount = 9
+	var input indexWriterSeriesSlice
+	for i := 1; i <= seriesCount; i++ {
+		input = append(input, &indexWriterSeries{
+			labels: labels.FromStrings("__name__", strconv.Itoa(i)),
+			chunks: []chunks.Meta{
+				{Ref: 1, MinTime: 0, MaxTime: 10},
+			},
+		})
+	}
+	ir, _, _ := createFileReader(context.Background(), t, input)
+
+	p := ir.PostingsForAllLabelValues(context.Background(), "__name__")
+	require.NoError(t, p.Err())
+	refs, err := ExpandPostings(p)
+	require.NoError(t, err)
+	require.Equal(t, []storage.SeriesRef{3, 4, 5, 6, 7, 8, 9, 10, 11}, refs)
+}
+
 func TestReader_PostingsForLabelMatchingHonorsContextCancel(t *testing.T) {
 	const seriesCount = 1000
 	var input indexWriterSeriesSlice

tsdb/index/postings.go

@@ -447,6 +447,22 @@ func (p *MemPostings) PostingsForLabelMatching(ctx context.Context, name string,
 	return Merge(ctx, its...)
 }
 
+func (p *MemPostings) PostingsForAllLabelValues(ctx context.Context, name string) Postings {
+	p.mtx.RLock()
+
+	e := p.m[name]
+	its := make([]Postings, 0, len(e))
+	for _, refs := range e {
+		if len(refs) > 0 {
+			its = append(its, NewListPostings(refs))
+		}
+	}
+
+	// Let the mutex go before merging.
+	p.mtx.RUnlock()
+	return Merge(ctx, its...)
+}
+
 // labelValues returns a slice of label values for the given label name.
 // It will take the read lock.
 func (p *MemPostings) labelValues(name string) []string {

tsdb/index/postings_test.go

@@ -1460,6 +1460,21 @@ func TestMemPostings_PostingsForLabelMatching(t *testing.T) {
 	require.Equal(t, []storage.SeriesRef{2, 4}, refs)
 }
 
+func TestMemPostings_PostingsForAllLabelValues(t *testing.T) {
+	mp := NewMemPostings()
+	mp.Add(1, labels.FromStrings("foo", "1"))
+	mp.Add(2, labels.FromStrings("foo", "2"))
+	mp.Add(3, labels.FromStrings("foo", "3"))
+	mp.Add(4, labels.FromStrings("foo", "4"))
+
+	p := mp.PostingsForAllLabelValues(context.Background(), "foo")
+	require.NoError(t, p.Err())
+	refs, err := ExpandPostings(p)
+	require.NoError(t, err)
+	// All postings for the label should be returned.
+	require.Equal(t, []storage.SeriesRef{1, 2, 3, 4}, refs)
+}
+
 func TestMemPostings_PostingsForLabelMatchingHonorsContextCancel(t *testing.T) {
 	memP := NewMemPostings()
 	seriesCount := 10 * checkContextEveryNIterations

tsdb/ooo_head_read.go

@@ -450,6 +450,10 @@ func (ir *OOOCompactionHeadIndexReader) PostingsForLabelMatching(context.Context
 	return index.ErrPostings(errors.New("not supported"))
 }
 
+func (ir *OOOCompactionHeadIndexReader) PostingsForAllLabelValues(context.Context, string) index.Postings {
+	return index.ErrPostings(errors.New("not supported"))
+}
+
 func (ir *OOOCompactionHeadIndexReader) SortedPostings(p index.Postings) index.Postings {
 	// This will already be sorted from the Postings() call above.
 	return p

tsdb/querier.go

@@ -365,29 +365,16 @@ func inversePostingsForMatcher(ctx context.Context, ix IndexReader, m *labels.Ma
 		return ix.Postings(ctx, m.Name, m.Value)
 	}
 
-	vals, err := ix.LabelValues(ctx, m.Name)
+	// If the matcher being inverted is =~"" or ="", we just want all the values.
-	if err != nil {
-		return nil, err
-	}
-
-	res := vals[:0]
-	// If the match before inversion was !="" or !~"", we just want all the values.
 	if m.Value == "" && (m.Type == labels.MatchRegexp || m.Type == labels.MatchEqual) {
-		res = vals
+		it := ix.PostingsForAllLabelValues(ctx, m.Name)
-	} else {
+		return it, it.Err()
-		count := 1
-		for _, val := range vals {
-			if count%checkContextEveryNIterations == 0 && ctx.Err() != nil {
-				return nil, ctx.Err()
-			}
-			count++
-			if !m.Matches(val) {
-				res = append(res, val)
-			}
-		}
 	}
 
-	return ix.Postings(ctx, m.Name, res...)
+	it := ix.PostingsForLabelMatching(ctx, m.Name, func(s string) bool {
+		return !m.Matches(s)
+	})
+	return it, it.Err()
 }
 
 func labelValuesWithMatchers(ctx context.Context, r IndexReader, name string, matchers ...*labels.Matcher) ([]string, error) {

tsdb/querier_test.go

@@ -2340,6 +2340,16 @@ func (m mockIndex) PostingsForLabelMatching(ctx context.Context, name string, ma
 	return index.Merge(ctx, res...)
 }
 
+func (m mockIndex) PostingsForAllLabelValues(ctx context.Context, name string) index.Postings {
+	var res []index.Postings
+	for l, srs := range m.postings {
+		if l.Name == name {
+			res = append(res, index.NewListPostings(srs))
+		}
+	}
+	return index.Merge(ctx, res...)
+}
+
 func (m mockIndex) ShardedPostings(p index.Postings, shardIndex, shardCount uint64) index.Postings {
 	out := make([]storage.SeriesRef, 0, 128)
 
@@ -3327,6 +3337,10 @@ func (m mockMatcherIndex) PostingsForLabelMatching(context.Context, string, func
 	return index.ErrPostings(errors.New("PostingsForLabelMatching called"))
 }
 
+func (m mockMatcherIndex) PostingsForAllLabelValues(context.Context, string) index.Postings {
+	return index.ErrPostings(errors.New("PostingsForAllLabelValues called"))
+}
+
 func TestPostingsForMatcher(t *testing.T) {
 	ctx := context.Background()
 
@@ -3725,17 +3739,6 @@ func TestReader_PostingsForLabelMatchingHonorsContextCancel(t *testing.T) {
 	require.Equal(t, failAfter+1, ctx.Count()) // Plus one for the Err() call that puts the error in the result.
 }
 
-func TestReader_InversePostingsForMatcherHonorsContextCancel(t *testing.T) {
-	ir := mockReaderOfLabels{}
-
-	failAfter := uint64(mockReaderOfLabelsSeriesCount / 2 / checkContextEveryNIterations)
-	ctx := &testutil.MockContextErrAfter{FailAfter: failAfter}
-	_, err := inversePostingsForMatcher(ctx, ir, labels.MustNewMatcher(labels.MatchRegexp, "__name__", ".*"))
-
-	require.Error(t, err)
-	require.Equal(t, failAfter+1, ctx.Count()) // Plus one for the Err() call that puts the error in the result.
-}
-
 type mockReaderOfLabels struct{}
 
 const mockReaderOfLabelsSeriesCount = checkContextEveryNIterations * 10
@@ -3768,6 +3771,10 @@ func (m mockReaderOfLabels) PostingsForLabelMatching(context.Context, string, fu
 	panic("PostingsForLabelMatching called")
 }
 
+func (m mockReaderOfLabels) PostingsForAllLabelValues(context.Context, string) index.Postings {
+	panic("PostingsForAllLabelValues called")
+}
+
 func (m mockReaderOfLabels) Postings(context.Context, string, ...string) (index.Postings, error) {
 	panic("Postings called")
 }