tsdb: create SymbolTables for labels as required

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

model/textparse/openmetricsparse_test.go

@@ -400,7 +400,7 @@ choices}`, "strange©™\n'quoted' \"name\"", "6"),
 			require.Equal(t, exp[i].m, string(m))
 			require.Equal(t, exp[i].t, ts)
 			require.Equal(t, exp[i].v, v)
-			require.Equal(t, exp[i].lset, res)
+			testutil.RequireEqual(t, exp[i].lset, res)
 			if exp[i].e == nil {
 				require.False(t, found)
 			} else {

model/textparse/promparse_test.go

@@ -325,7 +325,7 @@ choices}`, "strange©™\n'quoted' \"name\"", "6"),
 			require.Equal(t, exp[i].m, string(m))
 			require.Equal(t, exp[i].t, ts)
 			require.Equal(t, exp[i].v, v)
-			require.Equal(t, exp[i].lset, res)
+			testutil.RequireEqual(t, exp[i].lset, res)
 
 		case EntryType:
 			m, typ := p.Type()

tsdb/agent/db.go

@@ -417,7 +417,8 @@ func (db *DB) replayWAL() error {
 
 func (db *DB) loadWAL(r *wlog.Reader, multiRef map[chunks.HeadSeriesRef]chunks.HeadSeriesRef) (err error) {
 	var (
-		dec     record.Decoder
+		syms    = labels.NewSymbolTable() // One table for the whole WAL.
+		dec     = record.NewDecoder(syms)
 		lastRef = chunks.HeadSeriesRef(db.nextRef.Load())
 
 		decoded = make(chan interface{}, 10)

tsdb/head.go

@@ -717,6 +717,7 @@ func (h *Head) Init(minValidTime int64) error {
 
 	h.startWALReplayStatus(startFrom, endAt)
 
+	syms := labels.NewSymbolTable() // One table for the whole WAL.
 	multiRef := map[chunks.HeadSeriesRef]chunks.HeadSeriesRef{}
 	if err == nil && startFrom >= snapIdx {
 		sr, err := wlog.NewSegmentsReader(dir)
@@ -731,7 +732,7 @@ func (h *Head) Init(minValidTime int64) error {
 
 		// A corrupted checkpoint is a hard error for now and requires user
 		// intervention. There's likely little data that can be recovered anyway.
-		if err := h.loadWAL(wlog.NewReader(sr), multiRef, mmappedChunks, oooMmappedChunks); err != nil {
+		if err := h.loadWAL(wlog.NewReader(sr), syms, multiRef, mmappedChunks, oooMmappedChunks); err != nil {
 			return fmt.Errorf("backfill checkpoint: %w", err)
 		}
 		h.updateWALReplayStatusRead(startFrom)
@@ -764,7 +765,7 @@ func (h *Head) Init(minValidTime int64) error {
 		if err != nil {
 			return fmt.Errorf("segment reader (offset=%d): %w", offset, err)
 		}
-		err = h.loadWAL(wlog.NewReader(sr), multiRef, mmappedChunks, oooMmappedChunks)
+		err = h.loadWAL(wlog.NewReader(sr), syms, multiRef, mmappedChunks, oooMmappedChunks)
 		if err := sr.Close(); err != nil {
 			level.Warn(h.logger).Log("msg", "Error while closing the wal segments reader", "err", err)
 		}
@@ -792,7 +793,7 @@ func (h *Head) Init(minValidTime int64) error {
 			}
 
 			sr := wlog.NewSegmentBufReader(s)
-			err = h.loadWBL(wlog.NewReader(sr), multiRef, lastMmapRef)
+			err = h.loadWBL(wlog.NewReader(sr), syms, multiRef, lastMmapRef)
 			if err := sr.Close(); err != nil {
 				level.Warn(h.logger).Log("msg", "Error while closing the wbl segments reader", "err", err)
 			}

tsdb/head_wal.go

@@ -52,7 +52,7 @@ type histogramRecord struct {
 	fh  *histogram.FloatHistogram
 }
 
-func (h *Head) loadWAL(r *wlog.Reader, multiRef map[chunks.HeadSeriesRef]chunks.HeadSeriesRef, mmappedChunks, oooMmappedChunks map[chunks.HeadSeriesRef][]*mmappedChunk) (err error) {
+func (h *Head) loadWAL(r *wlog.Reader, syms *labels.SymbolTable, multiRef map[chunks.HeadSeriesRef]chunks.HeadSeriesRef, mmappedChunks, oooMmappedChunks map[chunks.HeadSeriesRef][]*mmappedChunk) (err error) {
 	// Track number of samples that referenced a series we don't know about
 	// for error reporting.
 	var unknownRefs atomic.Uint64
@@ -69,7 +69,6 @@ func (h *Head) loadWAL(r *wlog.Reader, multiRef map[chunks.HeadSeriesRef]chunks.
 		processors     = make([]walSubsetProcessor, concurrency)
 		exemplarsInput chan record.RefExemplar
 
-		dec             record.Decoder
 		shards          = make([][]record.RefSample, concurrency)
 		histogramShards = make([][]histogramRecord, concurrency)
 
@@ -137,6 +136,7 @@ func (h *Head) loadWAL(r *wlog.Reader, multiRef map[chunks.HeadSeriesRef]chunks.
 	go func() {
 		defer close(decoded)
 		var err error
+		dec := record.NewDecoder(syms)
 		for r.Next() {
 			rec := r.Record()
 			switch dec.Type(rec) {
@@ -645,7 +645,7 @@ func (wp *walSubsetProcessor) processWALSamples(h *Head, mmappedChunks, oooMmapp
 	return unknownRefs, unknownHistogramRefs, mmapOverlappingChunks
 }
 
-func (h *Head) loadWBL(r *wlog.Reader, multiRef map[chunks.HeadSeriesRef]chunks.HeadSeriesRef, lastMmapRef chunks.ChunkDiskMapperRef) (err error) {
+func (h *Head) loadWBL(r *wlog.Reader, syms *labels.SymbolTable, multiRef map[chunks.HeadSeriesRef]chunks.HeadSeriesRef, lastMmapRef chunks.ChunkDiskMapperRef) (err error) {
 	// Track number of samples, m-map markers, that referenced a series we don't know about
 	// for error reporting.
 	var unknownRefs, mmapMarkerUnknownRefs atomic.Uint64
@@ -657,7 +657,7 @@ func (h *Head) loadWBL(r *wlog.Reader, multiRef map[chunks.HeadSeriesRef]chunks.
 		concurrency = h.opts.WALReplayConcurrency
 		processors  = make([]wblSubsetProcessor, concurrency)
 
-		dec    record.Decoder
+		dec    = record.NewDecoder(syms)
 		shards = make([][]record.RefSample, concurrency)
 
 		decodedCh   = make(chan interface{}, 10)
@@ -1360,7 +1360,8 @@ func (h *Head) loadChunkSnapshot() (int, int, map[chunks.HeadSeriesRef]*memSerie
 		errChan          = make(chan error, concurrency)
 		refSeries        map[chunks.HeadSeriesRef]*memSeries
 		exemplarBuf      []record.RefExemplar
-		dec              record.Decoder
+		syms             = labels.NewSymbolTable() // New table for the whole snapshot.
+		dec              = record.NewDecoder(syms)
 	)
 
 	wg.Add(concurrency)

tsdb/index/index.go

@@ -1118,6 +1118,7 @@ type Reader struct {
 	symbols     *Symbols
 	nameSymbols map[uint32]string // Cache of the label name symbol lookups,
 	// as there are not many and they are half of all lookups.
+	st *labels.SymbolTable // TODO: see if we can merge this with nameSymbols.
 
 	dec *Decoder
 
@@ -1177,6 +1178,7 @@ func newReader(b ByteSlice, c io.Closer) (*Reader, error) {
 		b:        b,
 		c:        c,
 		postings: map[string][]postingOffset{},
+		st:       labels.NewSymbolTable(),
 	}
 
 	// Verify header.
@@ -1653,6 +1655,8 @@ func (r *Reader) Series(id storage.SeriesRef, builder *labels.ScratchBuilder, ch
 	if d.Err() != nil {
 		return d.Err()
 	}
+	builder.SetSymbolTable(r.st)
+	builder.Reset()
 	err := r.dec.Series(d.Get(), builder, chks)
 	if err != nil {
 		return fmt.Errorf("read series: %w", err)

tsdb/record/record.go

@@ -192,11 +192,14 @@ type RefMmapMarker struct {
 }
 
 // Decoder decodes series, sample, metadata and tombstone records.
-// The zero value is ready to use.
 type Decoder struct {
 	builder labels.ScratchBuilder
 }
 
+func NewDecoder(t *labels.SymbolTable) Decoder { // FIXME remove t
+	return Decoder{builder: labels.NewScratchBuilder(0)}
+}
+
 // Type returns the type of the record.
 // Returns RecordUnknown if no valid record type is found.
 func (d *Decoder) Type(rec []byte) Type {

tsdb/wal.go

@@ -31,6 +31,7 @@ import (
 	"github.com/go-kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
 
+	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/storage"
 	"github.com/prometheus/prometheus/tsdb/chunks"
 	"github.com/prometheus/prometheus/tsdb/encoding"
@@ -859,6 +860,7 @@ func newWALReader(files []*segmentFile, l log.Logger) *walReader {
 		files:  files,
 		buf:    make([]byte, 0, 128*4096),
 		crc32:  newCRC32(),
+		dec:    record.NewDecoder(labels.NewSymbolTable()),
 	}
 }
 

tsdb/wlog/checkpoint.go

@@ -28,6 +28,7 @@ import (
 	"github.com/go-kit/log/level"
 	"golang.org/x/exp/slices"
 
+	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/tsdb/chunks"
 	tsdb_errors "github.com/prometheus/prometheus/tsdb/errors"
 	"github.com/prometheus/prometheus/tsdb/fileutil"
@@ -154,7 +155,8 @@ func Checkpoint(logger log.Logger, w *WL, from, to int, keep func(id chunks.Head
 		tstones          []tombstones.Stone
 		exemplars        []record.RefExemplar
 		metadata         []record.RefMetadata
-		dec              record.Decoder
+		st               = labels.NewSymbolTable() // Needed for decoding; labels do not outlive this function.
+		dec              = record.NewDecoder(st)
 		enc              record.Encoder
 		buf              []byte
 		recs             [][]byte

tsdb/wlog/watcher.go

@@ -29,6 +29,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"golang.org/x/exp/slices"
 
+	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/model/timestamp"
 	"github.com/prometheus/prometheus/tsdb/record"
 )
@@ -532,7 +533,7 @@ func (w *Watcher) garbageCollectSeries(segmentNum int) error {
 // Also used with readCheckpoint - implements segmentReadFn.
 func (w *Watcher) readSegment(r *LiveReader, segmentNum int, tail bool) error {
 	var (
-		dec                   record.Decoder
+		dec                   = record.NewDecoder(labels.NewSymbolTable()) // One table per WAL segment means it won't grow indefinitely.
 		series                []record.RefSeries
 		samples               []record.RefSample
 		samplesToSend         []record.RefSample
@@ -669,7 +670,7 @@ func (w *Watcher) readSegment(r *LiveReader, segmentNum int, tail bool) error {
 // Used with readCheckpoint - implements segmentReadFn.
 func (w *Watcher) readSegmentForGC(r *LiveReader, segmentNum int, _ bool) error {
 	var (
-		dec    record.Decoder
+		dec    = record.NewDecoder(labels.NewSymbolTable()) // Needed for decoding; labels do not outlive this function.
 		series []record.RefSeries
 	)
 	for r.Next() && !isClosed(w.quit) {