Merge pull request #13276 from fpetkovski/reuse-float-histograms

Reuse float histogram objects

promql/engine.go

@@ -2078,21 +2078,27 @@ loop:
 		case chunkenc.ValNone:
 			break loop
 		case chunkenc.ValFloatHistogram, chunkenc.ValHistogram:
-			t, h := buf.AtFloatHistogram()
-			if value.IsStaleNaN(h.Sum) {
-				continue loop
-			}
+			t := buf.AtT()
 			// Values in the buffer are guaranteed to be smaller than maxt.
 			if t >= mintHistograms {
-				if ev.currentSamples >= ev.maxSamples {
-					ev.error(ErrTooManySamples(env))
-				}
-				point := HPoint{T: t, H: h}
 				if histograms == nil {
 					histograms = getHPointSlice(16)
 				}
-				histograms = append(histograms, point)
-				ev.currentSamples += point.size()
+				n := len(histograms)
+				if n < cap(histograms) {
+					histograms = histograms[:n+1]
+				} else {
+					histograms = append(histograms, HPoint{})
+				}
+				histograms[n].T, histograms[n].H = buf.AtFloatHistogram(histograms[n].H)
+				if value.IsStaleNaN(histograms[n].H.Sum) {
+					histograms = histograms[:n]
+					continue loop
+				}
+				if ev.currentSamples >= ev.maxSamples {
+					ev.error(ErrTooManySamples(env))
+				}
+				ev.currentSamples += histograms[n].size()
 			}
 		case chunkenc.ValFloat:
 			t, f := buf.At()

storage/buffer.go

@@ -74,7 +74,7 @@ func (b *BufferedSeriesIterator) PeekBack(n int) (sample chunks.Sample, ok bool)
 
 // Buffer returns an iterator over the buffered data. Invalidates previously
 // returned iterators.
-func (b *BufferedSeriesIterator) Buffer() chunkenc.Iterator {
+func (b *BufferedSeriesIterator) Buffer() *SampleRingIterator {
 	return b.buf.iterator()
 }
 
@@ -252,7 +252,7 @@ type sampleRing struct {
 	f int // Position of first element in ring buffer.
 	l int // Number of elements in buffer.
 
-	it sampleRingIterator
+	it SampleRingIterator
 }
 
 type bufType int
@@ -304,13 +304,15 @@ func (r *sampleRing) reset() {
 }
 
 // Returns the current iterator. Invalidates previously returned iterators.
-func (r *sampleRing) iterator() chunkenc.Iterator {
+func (r *sampleRing) iterator() *SampleRingIterator {
 	r.it.r = r
 	r.it.i = -1
 	return &r.it
 }
 
-type sampleRingIterator struct {
+// SampleRingIterator is returned by BufferedSeriesIterator.Buffer() and can be
+// used to iterate samples buffered in the lookback window.
+type SampleRingIterator struct {
 	r  *sampleRing
 	i  int
 	t  int64
@@ -319,7 +321,7 @@ type sampleRingIterator struct {
 	fh *histogram.FloatHistogram
 }
 
-func (it *sampleRingIterator) Next() chunkenc.ValueType {
+func (it *SampleRingIterator) Next() chunkenc.ValueType {
 	it.i++
 	if it.i >= it.r.l {
 		return chunkenc.ValNone
@@ -358,30 +360,28 @@ func (it *sampleRingIterator) Next() chunkenc.ValueType {
 	}
 }
 
-func (it *sampleRingIterator) Seek(int64) chunkenc.ValueType {
-	return chunkenc.ValNone
-}
-
-func (it *sampleRingIterator) Err() error {
-	return nil
-}
-
-func (it *sampleRingIterator) At() (int64, float64) {
+// At returns the current float element of the iterator.
+func (it *SampleRingIterator) At() (int64, float64) {
 	return it.t, it.f
 }
 
-func (it *sampleRingIterator) AtHistogram() (int64, *histogram.Histogram) {
+// AtHistogram returns the current histogram element of the iterator.
+func (it *SampleRingIterator) AtHistogram() (int64, *histogram.Histogram) {
 	return it.t, it.h
 }
 
-func (it *sampleRingIterator) AtFloatHistogram() (int64, *histogram.FloatHistogram) {
+// AtFloatHistogram returns the current histogram element of the iterator. If the
+// current sample is an integer histogram, it will be converted to a float histogram.
+// An optional histogram.FloatHistogram can be provided to avoid allocating a new
+// object for the conversion.
+func (it *SampleRingIterator) AtFloatHistogram(fh *histogram.FloatHistogram) (int64, *histogram.FloatHistogram) {
 	if it.fh == nil {
-		return it.t, it.h.ToFloat(nil)
+		return it.t, it.h.ToFloat(fh)
 	}
 	return it.t, it.fh
 }
 
-func (it *sampleRingIterator) AtT() int64 {
+func (it *SampleRingIterator) AtT() int64 {
 	return it.t
 }
 

storage/buffer_test.go

@@ -243,11 +243,11 @@ func TestBufferedSeriesIteratorMixedHistograms(t *testing.T) {
 	buf := it.Buffer()
 
 	require.Equal(t, chunkenc.ValFloatHistogram, buf.Next())
-	_, fh := buf.AtFloatHistogram()
+	_, fh := buf.AtFloatHistogram(nil)
 	require.Equal(t, histograms[0].ToFloat(nil), fh)
 
 	require.Equal(t, chunkenc.ValHistogram, buf.Next())
-	_, fh = buf.AtFloatHistogram()
+	_, fh = buf.AtFloatHistogram(nil)
 	require.Equal(t, histograms[1].ToFloat(nil), fh)
 }