lib/mergeset: optimize mergeInmemoryBlocks() function

Do not spend CPU time on converting inmemoryBlock structs to inmemoryPart structs.
Just merge inmemoryBlock structs directly.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2249

docs/CHANGELOG.md

@@ -20,6 +20,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
 * FEATURE: [vmauth](https://docs.victoriametrics.com/vmagent.html): allow multiple sections with duplicate `username` but with different `password` values at `-auth.config` file.
 * FEATURE: add ability to push internal metrics (e.g. metrics exposed at `/metrics` page) to the configured remote storage from all the VictoriaMetrics components. See [these docs](https://docs.victoriametrics.com/#push-metrics).
 * FEATURE: improve performance for heavy queries over big number of time series on systems with big number of CPU cores. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2896). Thanks to @zqyzyq for [the idea](https://github.com/VictoriaMetrics/VictoriaMetrics/commit/b596ac3745314fcc170a14e3ded062971cf7ced2).
+* FEATURE: improve performance for registering new time series in `indexdb` by up to 50%. Thanks to @ahfuzhang for [the issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2249).
 
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): set `up` metric to `0` for partial scrapes in [stream parsing mode](https://docs.victoriametrics.com/vmagent.html#stream-parsing-mode). Previously the `up` metric was set to `1` when at least a single metric has been scraped before the error. This aligns the behaviour of `vmselect` with Prometheus.
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): restart all the scrape jobs during [config reload](https://docs.victoriametrics.com/vmagent.html#configuration-update) after `global` section is changed inside `-promscrape.config`. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2884).

lib/mergeset/block_stream_reader.go

@@ -17,6 +17,9 @@ type blockStreamReader struct {
 	// Block contains the current block if Next returned true.
 	Block inmemoryBlock
 
+	// isInmemoryBlock is set to true if bsr was initialized with InitFromInmemoryBlock().
+	isInmemoryBlock bool
+
 	// The index of the current item in the Block, which is returned from CurrItem()
 	currItemIdx int
 
@@ -67,6 +70,7 @@ type blockStreamReader struct {
 
 func (bsr *blockStreamReader) reset() {
 	bsr.Block.Reset()
+	bsr.isInmemoryBlock = false
 	bsr.currItemIdx = 0
 	bsr.path = ""
 	bsr.ph.Reset()
@@ -99,6 +103,14 @@ func (bsr *blockStreamReader) String() string {
 	return bsr.ph.String()
 }
 
+// InitFromInmemoryBlock initializes bsr from the given ib.
+func (bsr *blockStreamReader) InitFromInmemoryBlock(ib *inmemoryBlock) {
+	bsr.reset()
+	bsr.Block.CopyFrom(ib)
+	bsr.Block.SortItems()
+	bsr.isInmemoryBlock = true
+}
+
 // InitFromInmemoryPart initializes bsr from the given mp.
 func (bsr *blockStreamReader) InitFromInmemoryPart(mp *inmemoryPart) {
 	bsr.reset()
@@ -179,10 +191,11 @@ func (bsr *blockStreamReader) InitFromFilePart(path string) error {
 //
 // It closes *Reader files passed to Init.
 func (bsr *blockStreamReader) MustClose() {
+	if !bsr.isInmemoryBlock {
 		bsr.indexReader.MustClose()
 		bsr.itemsReader.MustClose()
 		bsr.lensReader.MustClose()
-
+	}
 	bsr.reset()
 }
 
@@ -194,6 +207,10 @@ func (bsr *blockStreamReader) Next() bool {
 	if bsr.err != nil {
 		return false
 	}
+	if bsr.isInmemoryBlock {
+		bsr.err = io.EOF
+		return true
+	}
 
 	if bsr.bhIdx >= len(bsr.bhs) {
 		// The current index block is over. Try reading the next index block.

lib/mergeset/encoding.go

@@ -1,6 +1,7 @@
 package mergeset
 
 import (
+	"bytes"
 	"fmt"
 	"os"
 	"reflect"
@@ -36,7 +37,7 @@ func (it Item) Bytes(data []byte) []byte {
 	return data
 }
 
-// String returns string represetnation of it obtained from data.
+// String returns string representation of it obtained from data.
 //
 // The returned string representation belongs to data.
 func (it Item) String(data []byte) string {
@@ -56,7 +57,7 @@ func (ib *inmemoryBlock) Less(i, j int) bool {
 	a.Start += cpLen
 	b.Start += cpLen
 	data := ib.data
-	return string(a.Bytes(data)) < string(b.Bytes(data))
+	return a.String(data) < b.String(data)
 }
 
 func (ib *inmemoryBlock) Swap(i, j int) {
@@ -76,6 +77,21 @@ type inmemoryBlock struct {
 	items []Item
 }
 
+func (ib *inmemoryBlock) CopyFrom(src *inmemoryBlock) {
+	ib.commonPrefix = append(ib.commonPrefix[:0], src.commonPrefix...)
+	ib.data = append(ib.data[:0], src.data...)
+	ib.items = append(ib.items[:0], src.items...)
+}
+
+func (ib *inmemoryBlock) SortItems() {
+	if !ib.isSorted() {
+		ib.updateCommonPrefixUnsorted()
+		sort.Sort(ib)
+	} else {
+		ib.updateCommonPrefixSorted()
+	}
+}
+
 func (ib *inmemoryBlock) SizeBytes() int {
 	return int(unsafe.Sizeof(*ib)) + cap(ib.commonPrefix) + cap(ib.data) + cap(ib.items)*int(unsafe.Sizeof(Item{}))
 }
@@ -110,7 +126,11 @@ func (ib *inmemoryBlock) updateCommonPrefixUnsorted() {
 	data := ib.data
 	cp := items[0].Bytes(data)
 	for _, it := range items[1:] {
-		cpLen := commonPrefixLen(cp, it.Bytes(data))
+		item := it.Bytes(data)
+		if bytes.HasPrefix(item, cp) {
+			continue
+		}
+		cpLen := commonPrefixLen(cp, item)
 		if cpLen == 0 {
 			return
 		}
@@ -199,12 +219,7 @@ func (ib *inmemoryBlock) isSorted() bool {
 // - returns the number of items encoded including the first item.
 // - returns the marshal type used for the encoding.
 func (ib *inmemoryBlock) MarshalUnsortedData(sb *storageBlock, firstItemDst, commonPrefixDst []byte, compressLevel int) ([]byte, []byte, uint32, marshalType) {
-	if !ib.isSorted() {
-		ib.updateCommonPrefixUnsorted()
-		sort.Sort(ib)
-	} else {
-		ib.updateCommonPrefixSorted()
-	}
+	ib.SortItems()
 	return ib.marshalData(sb, firstItemDst, commonPrefixDst, compressLevel)
 }
 

lib/mergeset/table.go

@@ -718,23 +718,28 @@ func (tb *Table) mergeRawItemsBlocks(ibs []*inmemoryBlock, isFinal bool) {
 }
 
 func (tb *Table) mergeInmemoryBlocks(ibs []*inmemoryBlock) *partWrapper {
-	// Convert ibs into inmemoryPart's
-	mps := make([]*inmemoryPart, 0, len(ibs))
+	atomic.AddUint64(&tb.mergesCount, 1)
+	atomic.AddUint64(&tb.activeMerges, 1)
+	defer atomic.AddUint64(&tb.activeMerges, ^uint64(0))
+
+	// Prepare blockStreamReaders for source blocks.
+	bsrs := make([]*blockStreamReader, 0, len(ibs))
 	for _, ib := range ibs {
 		if len(ib.items) == 0 {
 			continue
 		}
-		mp := getInmemoryPart()
-		mp.Init(ib)
+		bsr := getBlockStreamReader()
+		bsr.InitFromInmemoryBlock(ib)
 		putInmemoryBlock(ib)
-		mps = append(mps, mp)
+		bsrs = append(bsrs, bsr)
 	}
-	if len(mps) == 0 {
+	if len(bsrs) == 0 {
 		return nil
 	}
-	if len(mps) == 1 {
+	if len(bsrs) == 1 {
 		// Nothing to merge. Just return a single inmemory part.
-		mp := mps[0]
+		mp := getInmemoryPart()
+		mp.Init(&bsrs[0].Block)
 		p := mp.NewPart()
 		return &partWrapper{
 			p:        p,
@@ -742,24 +747,6 @@ func (tb *Table) mergeInmemoryBlocks(ibs []*inmemoryBlock) *partWrapper {
 			refCount: 1,
 		}
 	}
-	defer func() {
-		// Return source inmemoryParts to pool.
-		for _, mp := range mps {
-			putInmemoryPart(mp)
-		}
-	}()
-
-	atomic.AddUint64(&tb.mergesCount, 1)
-	atomic.AddUint64(&tb.activeMerges, 1)
-	defer atomic.AddUint64(&tb.activeMerges, ^uint64(0))
-
-	// Prepare blockStreamReaders for source parts.
-	bsrs := make([]*blockStreamReader, 0, len(mps))
-	for _, mp := range mps {
-		bsr := getBlockStreamReader()
-		bsr.InitFromInmemoryPart(mp)
-		bsrs = append(bsrs, bsr)
-	}
 
 	// Prepare blockStreamWriter for destination part.
 	bsw := getBlockStreamWriter()