Increase max stack trace nodes per chunk limit

pkg/phlaredb/symdb/block_writer.go

@@ -136,13 +136,17 @@ func (w *writer) Flush() (err error) {
 
 func (w *writer) writeStacktraces(partition *PartitionWriter) (err error) {
 	for ci, c := range partition.stacktraces.chunks {
+		stacks := c.stacks
+		if stacks == 0 {
+			stacks = uint32(len(partition.stacktraces.hashToIdx))
+		}
 		h := StacktraceChunkHeader{
 			Offset:             w.stacktraces.w.offset,
 			Size:               0, // Set later.
 			Partition:          partition.header.Partition,
 			ChunkIndex:         uint16(ci),
 			ChunkEncoding:      ChunkEncodingGroupVarint,
-			Stacktraces:        c.stacks,
+			Stacktraces:        stacks,
 			StacktraceNodes:    c.tree.len(),
 			StacktraceMaxDepth: 0, // TODO
 			StacktraceMaxNodes: c.partition.maxNodesPerChunk,

pkg/phlaredb/symdb/symdb.go

@@ -110,10 +110,10 @@ func DefaultConfig() *Config {
 	return &Config{
 		Dir: DefaultDirName,
 		Stacktraces: StacktracesConfig{
-			// A million of nodes ensures predictable
-			// memory consumption, although causes a
-			// small overhead.
-			MaxNodesPerChunk: 1 << 20,
+			// At the moment chunks are loaded in memory at once.
+			// Due to the fact that chunking causes some duplication,
+			// it's better to keep them large.
+			MaxNodesPerChunk: 4 << 20,
 		},
 		Parquet: ParquetConfig{
 			MaxBufferRowCount: 100 << 10,

pkg/phlaredb/symdb/symdb_test.go

@@ -141,3 +141,39 @@ func treeFingerprint(t *phlaremodel.Tree) [][2]uint64 {
 	sort.Slice(m, func(i, j int) bool { return m[i][0] < m[j][0] })
 	return m
 }
+
+func Test_Stats(t *testing.T) {
+	s := memSuite{
+		t:     t,
+		files: [][]string{{"testdata/profile.pb.gz"}},
+		config: &Config{
+			Dir: t.TempDir(),
+			Stacktraces: StacktracesConfig{
+				MaxNodesPerChunk: 4 << 20,
+			},
+			Parquet: ParquetConfig{
+				MaxBufferRowCount: 100 << 10,
+			},
+		},
+	}
+
+	s.init()
+	bs := blockSuite{memSuite: &s}
+	bs.flush()
+	defer bs.teardown()
+
+	p, err := bs.reader.Partition(context.Background(), 0)
+	require.NoError(t, err)
+
+	var actual PartitionStats
+	p.WriteStats(&actual)
+	expected := PartitionStats{
+		StacktracesTotal: 611,
+		MaxStacktraceID:  1793,
+		LocationsTotal:   762,
+		MappingsTotal:    3,
+		FunctionsTotal:   507,
+		StringsTotal:     700,
+	}
+	require.Equal(t, expected, actual)
+}