app/vmselect/netstorage: do not spend CPU time on unpacking empty blocks during /api/v1/series calls

app/vmselect/netstorage/netstorage.go

@@ -180,7 +180,6 @@ type unpackWorkItem struct {
 type unpackWork struct {
 	ws     []unpackWorkItem
 	tbf    *tmpBlocksFile
-	fetchData bool
 	at     *auth.Token
 	sbs    []*sortBlock
 	doneCh chan error
@@ -195,7 +194,6 @@ func (upw *unpackWork) reset() {
 	}
 	upw.ws = upw.ws[:0]
 	upw.tbf = nil
-	upw.fetchData = false
 	upw.at = nil
 	sbs := upw.sbs
 	for i := range sbs {
@@ -210,7 +208,7 @@ func (upw *unpackWork) reset() {
 func (upw *unpackWork) unpack(tmpBlock *storage.Block) {
 	for _, w := range upw.ws {
 		sb := getSortBlock()
-		if err := sb.unpackFrom(tmpBlock, upw.tbf, w.addr, w.tr, upw.fetchData, upw.at); err != nil {
+		if err := sb.unpackFrom(tmpBlock, upw.tbf, w.addr, w.tr, upw.at); err != nil {
 			putSortBlock(sb)
 			upw.doneCh <- fmt.Errorf("cannot unpack block: %w", err)
 			return
@@ -258,17 +256,19 @@ var unpackBatchSize = 8 * runtime.GOMAXPROCS(-1)
 // Unpack unpacks pts to dst.
 func (pts *packedTimeseries) Unpack(tbf *tmpBlocksFile, dst *Result, tr storage.TimeRange, fetchData bool, at *auth.Token) error {
 	dst.reset()
-
 	if err := dst.MetricName.Unmarshal(bytesutil.ToUnsafeBytes(pts.metricName)); err != nil {
 		return fmt.Errorf("cannot unmarshal metricName %q: %w", pts.metricName, err)
 	}
+	if !fetchData {
+		// Do not spend resources on data reading and unpacking.
+		return nil
+	}
 
 	// Feed workers with work
 	addrsLen := len(pts.addrs)
 	upws := make([]*unpackWork, 0, 1+addrsLen/unpackBatchSize)
 	upw := getUnpackWork()
 	upw.tbf = tbf
-	upw.fetchData = fetchData
 	upw.at = at
 	for _, addr := range pts.addrs {
 		if len(upw.ws) >= unpackBatchSize {
@@ -276,7 +276,6 @@ func (pts *packedTimeseries) Unpack(tbf *tmpBlocksFile, dst *Result, tr storage.
 			upws = append(upws, upw)
 			upw = getUnpackWork()
 			upw.tbf = tbf
-			upw.fetchData = fetchData
 			upw.at = at
 		}
 		upw.ws = append(upw.ws, unpackWorkItem{
@@ -394,14 +393,12 @@ func (sb *sortBlock) reset() {
 	sb.NextIdx = 0
 }
 
-func (sb *sortBlock) unpackFrom(tmpBlock *storage.Block, tbf *tmpBlocksFile, addr tmpBlockAddr, tr storage.TimeRange, fetchData bool, at *auth.Token) error {
+func (sb *sortBlock) unpackFrom(tmpBlock *storage.Block, tbf *tmpBlocksFile, addr tmpBlockAddr, tr storage.TimeRange, at *auth.Token) error {
 	tmpBlock.Reset()
 	tbf.MustReadBlockAt(tmpBlock, addr)
-	if fetchData {
 	if err := tmpBlock.UnmarshalData(); err != nil {
 		return fmt.Errorf("cannot unmarshal block: %w", err)
 	}
-	}
 	timestamps := tmpBlock.Timestamps()
 
 	// Skip timestamps smaller than tr.MinTimestamp.
@@ -982,7 +979,19 @@ type tmpBlocksFileWrapper struct {
 	orderedMetricNames []string
 }
 
-func (tbfw *tmpBlocksFileWrapper) WriteBlock(mb *storage.MetricBlock) error {
+func (tbfw *tmpBlocksFileWrapper) RegisterEmptyBlock(mb *storage.MetricBlock) {
+	metricName := mb.MetricName
+	tbfw.mu.Lock()
+	if addrs := tbfw.m[string(metricName)]; addrs == nil {
+		// An optimization for big number of time series with long names: store only a single copy of metricNameStr
+		// in both tbfw.orderedMetricNames and tbfw.m.
+		tbfw.orderedMetricNames = append(tbfw.orderedMetricNames, string(metricName))
+		tbfw.m[tbfw.orderedMetricNames[len(tbfw.orderedMetricNames)-1]] = []tmpBlockAddr{{}}
+	}
+	tbfw.mu.Unlock()
+}
+
+func (tbfw *tmpBlocksFileWrapper) RegisterAndWriteBlock(mb *storage.MetricBlock) error {
 	bb := tmpBufPool.Get()
 	bb.B = storage.MarshalBlock(bb.B[:0], &mb.Block)
 	tbfw.mu.Lock()
@@ -1754,7 +1763,11 @@ func (sn *storageNode) processSearchQueryOnConn(tbfw *tmpBlocksFileWrapper, bc *
 		blocksRead++
 		sn.metricBlocksRead.Inc()
 		sn.metricRowsRead.Add(mb.Block.RowsCount())
-		if err := tbfw.WriteBlock(&mb); err != nil {
+		if !fetchData {
+			tbfw.RegisterEmptyBlock(&mb)
+			continue
+		}
+		if err := tbfw.RegisterAndWriteBlock(&mb); err != nil {
 			return blocksRead, fmt.Errorf("cannot write MetricBlock #%d to temporary blocks file: %w", blocksRead, err)
 		}
 	}