Use binary search in getSeriesIndex (#621)

* Use binary search in `getSeriesIndex`

* Add a test case, which will trigger the nil row range case

---------

Co-authored-by: Christian Simon <simon@swine.de>

pkg/phlaredb/profile_store_test.go

@@ -79,6 +79,36 @@ func sameProfileStream(i int) *testProfile {
 	return tp
 }
 
+// This will simulate a profile stream which ends and a new one starts at i > boundary
+func profileStreamEndingAndStarting(boundary int) func(int) *testProfile {
+	return func(i int) *testProfile {
+		tp := &testProfile{}
+
+		series := "at-beginning"
+		if i > boundary {
+			series = "at-end"
+		}
+
+		tp.profileName = "process_cpu:cpu:nanoseconds:cpu:nanoseconds"
+		tp.lbls = phlaremodel.LabelsFromStrings(
+			phlaremodel.LabelNameProfileType, tp.profileName,
+			"job", "test",
+			"stream", series,
+		)
+
+		tp.p.ID = uuid.MustParse(fmt.Sprintf("00000000-0000-0000-0000-%012d", i))
+		tp.p.TimeNanos = time.Second.Nanoseconds() * int64(i)
+		tp.p.Samples = []*schemav1.Sample{
+			{
+				StacktraceID: 0x1,
+				Value:        10.0,
+			},
+		}
+		tp.populateFingerprint()
+		return tp
+	}
+}
+
 func readFullParquetFile[M any](t *testing.T, path string) ([]M, uint64) {
 	f, err := os.Open(path)
 	require.NoError(t, err)
@@ -131,6 +161,13 @@ func TestProfileStore_RowGroupSplitting(t *testing.T) {
 			expectedNumRows: 100,
 			values:          sameProfileStream,
 		},
+		{
+			name:            "a stream ending after half of the samples and a new one starting",
+			cfg:             &ParquetConfig{MaxRowGroupBytes: 1828, MaxBufferRowCount: 100000},
+			expectedNumRGs:  10,
+			expectedNumRows: 100,
+			values:          profileStreamEndingAndStarting(50),
+		},
 		{
 			name:            "multiple row groups because of maximum row num",
 			cfg:             &ParquetConfig{MaxRowGroupBytes: 128000, MaxBufferRowCount: 10},

pkg/phlaredb/profiles.go

@@ -41,14 +41,20 @@ type rowRangeWithSeriesIndex struct {
 type rowRangesWithSeriesIndex []rowRangeWithSeriesIndex
 
 func (s rowRangesWithSeriesIndex) getSeriesIndex(rowNum int64) uint32 {
-	// todo: binary search
-	for _, rg := range s {
-		// it is possible that the series is not existing
-		if rg.rowRange == nil {
+	l, r := 0, len(s)-1
+	for l <= r {
+		mid := (l + r) / 2
+		if s[mid].rowRange == nil {
+			l = mid + 1
 			continue
 		}
-		if rg.rowNum <= rowNum && rg.rowNum+int64(rg.length) > rowNum {
-			return rg.seriesIndex
+		if s[mid].rowNum <= rowNum && s[mid].rowNum+int64(s[mid].length) > rowNum {
+			return s[mid].seriesIndex
+		}
+		if s[mid].rowNum > rowNum {
+			r = mid - 1
+		} else {
+			l = mid + 1
 		}
 	}
 	panic("series index not found")

pkg/pprof/pprof.go

@@ -182,9 +182,9 @@ func FromProfile(p *profile.Profile) (*profilev1.Profile, error) {
 		r.Mapping = append(r.Mapping, &profilev1.Mapping{
 			Id:              m.ID,
 			Filename:        addString(strings, m.File),
-			MemoryStart:     (m.Start),
-			MemoryLimit:     (m.Limit),
-			FileOffset:      (m.Offset),
+			MemoryStart:     m.Start,
+			MemoryLimit:     m.Limit,
+			FileOffset:      m.Offset,
 			BuildId:         addString(strings, m.BuildID),
 			HasFunctions:    m.HasFunctions,
 			HasFilenames:    m.HasFilenames,