Add a NotCounterReset flag

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

tsdb/chunkenc/chunk.go

@@ -82,7 +82,7 @@ type Chunk interface {
 // Appender adds sample pairs to a chunk.
 type Appender interface {
 	Append(int64, float64)
-	AppendHistogram(t int64, h histogram.SparseHistogram, counterReset bool)
+	AppendHistogram(t int64, h histogram.SparseHistogram)
 }
 
 // Iterator is a simple iterator that can only get the next value.

tsdb/chunkenc/histo.go

@@ -98,7 +98,7 @@ func (c *HistoChunk) NumSamples() int {
 
 // Meta returns the histogram metadata.
 // callers may only call this on chunks that have at least one sample
-func (c *HistoChunk) Meta() (bool, int32, float64, []histogram.Span, []histogram.Span, error) {
+func (c *HistoChunk) Meta() (int32, float64, []histogram.Span, []histogram.Span, error) {
 	if c.NumSamples() == 0 {
 		panic("HistoChunk.Meta() called on an empty chunk")
 	}
@@ -106,6 +106,18 @@ func (c *HistoChunk) Meta() (bool, int32, float64, []histogram.Span, []histogram
 	return readHistoChunkMeta(&b)
 }
 
+// SetCounterReset sets the counter reset flag to 1 if the passed argument is true, 0 otherwise.
+func (c *HistoChunk) SetCounterReset(counterReset bool) {
+	bytes := c.Bytes()
+	header := bytes[2]
+	if counterReset {
+		header |= counterResetMask
+	} else if (header & counterResetMask) != 0 {
+		header ^= counterResetMask
+	}
+	bytes[2] = header
+}
+
 // CounterReset returns true if this new chunk was created because of a counter reset.
 func (c *HistoChunk) CounterReset() bool {
 	if c.NumSamples() == 0 {
@@ -114,6 +126,27 @@ func (c *HistoChunk) CounterReset() bool {
 	return (c.Bytes()[2] & counterResetMask) != 0
 }
 
+// SetNotCounterReset sets the "not counter reset" flag to 1 if the passed argument is true, 0 otherwise.
+func (c *HistoChunk) SetNotCounterReset(notCounterReset bool) {
+	bytes := c.Bytes()
+	header := bytes[2]
+	if notCounterReset {
+		header |= notCounterResetMask
+	} else if (header & notCounterResetMask) != 0 {
+		header ^= notCounterResetMask
+	}
+	bytes[2] = header
+}
+
+// NotCounterReset returns true if this new chunk definitely did not have counter reset
+// from the earlier chunk.
+func (c *HistoChunk) NotCounterReset() bool {
+	if c.NumSamples() == 0 {
+		panic("HistoChunk.NotCounterReset() called on an empty chunk")
+	}
+	return (c.Bytes()[2] & notCounterResetMask) != 0
+}
+
 // Compact implements the Chunk interface.
 func (c *HistoChunk) Compact() {
 	if l := len(c.b.stream); cap(c.b.stream) > l+chunkCompactCapacityThreshold {
@@ -208,7 +241,6 @@ type HistoAppender struct {
 	b *bstream
 
 	// Metadata:
-	counterReset       bool
 	schema             int32
 	zeroThreshold      float64
 	posSpans, negSpans []histogram.Span
@@ -260,6 +292,7 @@ func (a *HistoAppender) Append(int64, float64) {}
 // * the last sample in the chunk was stale while the current sample is not stale
 // It returns an additional boolean set to true if it is not appendable because of a counter reset.
 // If the given sample is stale, it will always return true.
+// If counterReset is true, okToAppend MUST be false.
 func (a *HistoAppender) Appendable(h histogram.SparseHistogram) (posInterjections []Interjection, negInterjections []Interjection, okToAppend bool, counterReset bool) {
 	if value.IsStaleNaN(h.Sum) {
 		// This is a stale sample whose buckets and spans don't matter.
@@ -380,7 +413,7 @@ func counterResetInAnyBucket(oldBuckets, newBuckets []int64, oldSpans, newSpans
 // histogram is properly structured. E.g. that the number of pos/neg buckets
 // used corresponds to the number conveyed by the pos/neg span structures.
 // callers must call Appendable() first and act accordingly!
-func (a *HistoAppender) AppendHistogram(t int64, h histogram.SparseHistogram, counterReset bool) {
+func (a *HistoAppender) AppendHistogram(t int64, h histogram.SparseHistogram) {
 	var tDelta, cntDelta, zcntDelta int64
 	num := binary.BigEndian.Uint16(a.b.bytes())
 
@@ -390,17 +423,12 @@ func (a *HistoAppender) AppendHistogram(t int64, h histogram.SparseHistogram, co
 		h = histogram.SparseHistogram{Sum: h.Sum}
 	}
 
-	if num != 0 && counterReset {
-		panic("got counterReset=true for partially filled chunk in HistoAppender.AppendHistogram")
-	}
-
 	switch num {
 	case 0:
 		// the first append gets the privilege to dictate the metadata
 		// but it's also responsible for encoding it into the chunk!
 
-		writeHistoChunkMeta(a.b, counterReset, h.Schema, h.ZeroThreshold, h.PositiveSpans, h.NegativeSpans)
-		a.counterReset = true
+		writeHistoChunkMeta(a.b, h.Schema, h.ZeroThreshold, h.PositiveSpans, h.NegativeSpans)
 		a.schema = h.Schema
 		a.zeroThreshold = h.ZeroThreshold
 		a.posSpans, a.negSpans = h.PositiveSpans, h.NegativeSpans
@@ -503,7 +531,8 @@ func (a *HistoAppender) Recode(posInterjections, negInterjections []Interjection
 	// it again with the new span layout. This can probably be done in-place
 	// by editing the chunk. But let's first see how expensive it is in the
 	// big picture.
-	it := newHistoIterator(a.b.bytes())
+	byts := a.b.bytes()
+	it := newHistoIterator(byts)
 	hc := NewHistoChunk()
 	app, err := hc.Appender()
 	if err != nil {
@@ -511,7 +540,6 @@ func (a *HistoAppender) Recode(posInterjections, negInterjections []Interjection
 	}
 	numPosBuckets, numNegBuckets := countSpans(posSpans), countSpans(negSpans)
 
-	counterReset := a.counterReset
 	for it.Next() {
 		tOld, hOld := it.AtHistogram()
 
@@ -530,10 +558,12 @@ func (a *HistoAppender) Recode(posInterjections, negInterjections []Interjection
 		if len(negInterjections) > 0 {
 			hOld.NegativeBuckets = interject(hOld.NegativeBuckets, negBuckets, negInterjections)
 		}
-		app.AppendHistogram(tOld, hOld, counterReset)
-
-		counterReset = false // We need it only for the first sample.
+		app.AppendHistogram(tOld, hOld)
 	}
+
+	// Set the flags.
+	hc.SetCounterReset(byts[2]&counterResetMask != 0)
+	hc.SetNotCounterReset(byts[2]&notCounterResetMask != 0)
 	return hc, app
 }
 
@@ -674,7 +704,7 @@ func (it *histoIterator) Next() bool {
 
 		// first read is responsible for reading chunk metadata and initializing fields that depend on it
 		// We give counter reset info at chunk level, hence we discard it here.
-		_, schema, zeroThreshold, posSpans, negSpans, err := readHistoChunkMeta(&it.br)
+		schema, zeroThreshold, posSpans, negSpans, err := readHistoChunkMeta(&it.br)
 		if err != nil {
 			it.err = err
 			return false

tsdb/chunkenc/histo_meta.go

@@ -18,16 +18,11 @@ import (
 )
 
 const (
-	counterResetMask = 0b10000000
+	counterResetMask    = 0b10000000
+	notCounterResetMask = 0b01000000
 )
 
-func writeHistoChunkMeta(b *bstream, counterReset bool, schema int32, zeroThreshold float64, posSpans, negSpans []histogram.Span) {
-	header := byte(0)
-	if counterReset {
-		header |= counterResetMask
-	}
-	b.bytes()[2] = header
-
+func writeHistoChunkMeta(b *bstream, schema int32, zeroThreshold float64, posSpans, negSpans []histogram.Span) {
 	putInt64VBBucket(b, int64(schema))
 	putFloat64VBBucket(b, zeroThreshold)
 	putHistoChunkMetaSpans(b, posSpans)
@@ -42,15 +37,12 @@ func putHistoChunkMetaSpans(b *bstream, spans []histogram.Span) {
 	}
 }
 
-func readHistoChunkMeta(b *bstreamReader) (counterReset bool, schema int32, zeroThreshold float64, posSpans []histogram.Span, negSpans []histogram.Span, err error) {
-	var header byte
-	header, err = b.ReadByte()
+func readHistoChunkMeta(b *bstreamReader) (schema int32, zeroThreshold float64, posSpans []histogram.Span, negSpans []histogram.Span, err error) {
+	_, err = b.ReadByte() // The header.
 	if err != nil {
 		return
 	}
 
-	counterReset = (header & counterResetMask) != 0
-
 	v, err := readInt64VBBucket(b)
 	if err != nil {
 		return

tsdb/chunkenc/histo_test.go

@@ -42,7 +42,7 @@ func TestHistoChunkSameBuckets(t *testing.T) {
 		},
 		PositiveBuckets: []int64{1, 1, -1, 0}, // counts: 1, 2, 1, 1 (total 5)
 	}
-	app.AppendHistogram(ts, h, false)
+	app.AppendHistogram(ts, h)
 	exp = append(exp, res{t: ts, h: h})
 	require.Equal(t, 1, c.NumSamples())
 
@@ -52,7 +52,7 @@ func TestHistoChunkSameBuckets(t *testing.T) {
 	h.ZeroCount++
 	h.Sum = 24.4
 	h.PositiveBuckets = []int64{5, -2, 1, -2} // counts: 5, 3, 4, 2 (total 14)
-	app.AppendHistogram(ts, h, false)
+	app.AppendHistogram(ts, h)
 	exp = append(exp, res{t: ts, h: h})
 	require.Equal(t, 2, c.NumSamples())
 
@@ -65,7 +65,7 @@ func TestHistoChunkSameBuckets(t *testing.T) {
 	h.ZeroCount += 2
 	h.Sum = 24.4
 	h.PositiveBuckets = []int64{6, 1, -3, 6} // counts: 6, 7, 4, 10 (total 27)
-	app.AppendHistogram(ts, h, false)
+	app.AppendHistogram(ts, h)
 	exp = append(exp, res{t: ts, h: h})
 	require.Equal(t, 3, c.NumSamples())
 
@@ -142,7 +142,7 @@ func TestHistoChunkBucketChanges(t *testing.T) {
 		PositiveBuckets: []int64{6, -3, 0, -1, 2, 1, -4}, // counts: 6, 3, 3, 2, 4, 5, 1 (total 24)
 	}
 
-	app.AppendHistogram(ts1, h1, false)
+	app.AppendHistogram(ts1, h1)
 	require.Equal(t, 1, c.NumSamples())
 
 	// Add a new histogram that has expanded buckets.
@@ -169,7 +169,7 @@ func TestHistoChunkBucketChanges(t *testing.T) {
 	require.True(t, ok) // Only new buckets came in.
 	require.False(t, cr)
 	c, app = histoApp.Recode(posInterjections, negInterjections, h2.PositiveSpans, h2.NegativeSpans)
-	app.AppendHistogram(ts2, h2, false)
+	app.AppendHistogram(ts2, h2)
 
 	require.Equal(t, 2, c.NumSamples())
 
@@ -216,7 +216,7 @@ func TestHistoChunkAppendable(t *testing.T) {
 		PositiveBuckets: []int64{6, -3, 0, -1, 2, 1, -4}, // counts: 6, 3, 3, 2, 4, 5, 1 (total 24)
 	}
 
-	app.AppendHistogram(ts, h1, false)
+	app.AppendHistogram(ts, h1)
 	require.Equal(t, 1, c.NumSamples())
 
 	{ // New histogram that has more buckets.

tsdb/chunkenc/xor.go

@@ -150,7 +150,7 @@ type xorAppender struct {
 	trailing uint8
 }
 
-func (a *xorAppender) AppendHistogram(t int64, h histogram.SparseHistogram, counterReset bool) {
+func (a *xorAppender) AppendHistogram(t int64, h histogram.SparseHistogram) {
 	//panic("cannot call xorAppender.AppendHistogram().")
 }
 

tsdb/head_append.go

@@ -611,10 +611,10 @@ func (s *memSeries) appendHistogram(t int64, sh histogram.SparseHistogram, appen
 	app, _ := s.app.(*chunkenc.HistoAppender)
 	var (
 		posInterjections, negInterjections []chunkenc.Interjection
-		ok, counterReset                   bool
+		okToAppend, counterReset           bool
 	)
 	if app != nil {
-		posInterjections, negInterjections, ok, counterReset = app.Appendable(sh)
+		posInterjections, negInterjections, okToAppend, counterReset = app.Appendable(sh)
 	}
 
 	c, sampleInOrder, chunkCreated := s.appendPreprocessor(t, chunkenc.EncSHS, chunkDiskMapper)
@@ -623,11 +623,11 @@ func (s *memSeries) appendHistogram(t int64, sh histogram.SparseHistogram, appen
 	}
 
 	if !chunkCreated {
-		// we have 3 cases here
-		// !ok -> we need to cut a new chunk
-		// ok but we have interjections -> existing chunk needs recoding before we can append our histogram
-		// ok and no interjections -> chunk is ready to support our histogram
-		if !ok {
+		// We have 3 cases here
+		// !okToAppend -> we need to cut a new chunk
+		// okToAppend but we have interjections -> existing chunk needs recoding before we can append our histogram
+		// okToAppend and no interjections -> chunk is ready to support our histogram
+		if !okToAppend || counterReset {
 			c = s.cutNewHeadChunk(t, chunkenc.EncSHS, chunkDiskMapper)
 			chunkCreated = true
 		} else if len(posInterjections) > 0 || len(negInterjections) > 0 {
@@ -642,7 +642,16 @@ func (s *memSeries) appendHistogram(t int64, sh histogram.SparseHistogram, appen
 		}
 	}
 
-	s.app.AppendHistogram(t, sh, counterReset)
+	if chunkCreated {
+		hc := s.headChunk.chunk.(*chunkenc.HistoChunk)
+		if counterReset {
+			hc.SetCounterReset(true)
+		} else if okToAppend {
+			hc.SetNotCounterReset(true)
+		}
+	}
+
+	s.app.AppendHistogram(t, sh)
 	s.sparseHistogramSeries = true
 
 	c.maxTime = t

tsdb/querier.go

@@ -717,16 +717,16 @@ func (p *populateWithDelChunkSeriesIterator) Next() bool {
 		h histogram.SparseHistogram
 	)
 	if p.currDelIter.ChunkEncoding() == chunkenc.EncSHS {
-		counterReset := false
 		if hc, ok := p.currChkMeta.Chunk.(*chunkenc.HistoChunk); ok {
-			counterReset = hc.CounterReset()
+			newChunk.(*chunkenc.HistoChunk).SetCounterReset(hc.CounterReset())
+			newChunk.(*chunkenc.HistoChunk).SetNotCounterReset(hc.NotCounterReset())
 		}
 		t, h = p.currDelIter.AtHistogram()
 		p.curr.MinTime = t
-		app.AppendHistogram(t, h.Copy(), counterReset)
+		app.AppendHistogram(t, h.Copy())
 		for p.currDelIter.Next() {
 			t, h = p.currDelIter.AtHistogram()
-			app.AppendHistogram(t, h.Copy(), false)
+			app.AppendHistogram(t, h.Copy())
 		}
 	} else {
 		t, v = p.currDelIter.At()