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https://github.com/prometheus/prometheus.git
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model: Implement FloatHistogram.Compact
Signed-off-by: beorn7 <beorn@grafana.com>
This commit is contained in:
beorn7
parent
86cc83b13c
commit
3b4d6c3fdb
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@ -305,14 +305,164 @@ func addBucket(
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// Compact eliminates empty buckets at the beginning and end of each span, then
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// merges spans that are consecutive or at most maxEmptyBuckets apart, and
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// finally splits spans that contain more than maxEmptyBuckets. The compaction
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// happens "in place" in the receiving histogram, but a pointer to it is
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// returned for convenience.
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// finally splits spans that contain more consecutive empty buckets than
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// maxEmptyBuckets. (The actual implementation might do something more efficient
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// but with the same result.) The compaction happens "in place" in the
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// receiving histogram, but a pointer to it is returned for convenience.
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func (h *FloatHistogram) Compact(maxEmptyBuckets int) *FloatHistogram {
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// TODO(beorn7): Implement.
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h.PositiveBuckets, h.PositiveSpans = compactBuckets(
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h.PositiveBuckets, h.PositiveSpans, maxEmptyBuckets,
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)
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h.NegativeBuckets, h.NegativeSpans = compactBuckets(
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h.NegativeBuckets, h.NegativeSpans, maxEmptyBuckets,
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)
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return h
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}
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func compactBuckets(buckets []float64, spans []Span, maxEmptyBuckets int) ([]float64, []Span) {
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if len(buckets) == 0 {
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return buckets, spans
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}
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var iBucket, iSpan int
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var posInSpan uint32
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// Helper function.
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emptyBucketsHere := func() int {
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i := 0
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for i+iBucket < len(buckets) &&
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uint32(i)+posInSpan < spans[iSpan].Length &&
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buckets[i+iBucket] == 0 {
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i++
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}
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return i
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}
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// Merge spans with zero-offset to avoid special cases later.
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if len(spans) > 1 {
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for i, span := range spans[1:] {
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if span.Offset == 0 {
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spans[iSpan].Length += span.Length
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continue
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}
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iSpan++
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if i+1 != iSpan {
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spans[iSpan] = span
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}
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}
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spans = spans[:iSpan+1]
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iSpan = 0
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}
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// Merge spans with zero-length to avoid special cases later.
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for i, span := range spans {
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if span.Length == 0 {
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if i+1 < len(spans) {
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spans[i+1].Offset += span.Offset
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}
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continue
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}
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if i != iSpan {
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spans[iSpan] = span
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}
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iSpan++
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}
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spans = spans[:iSpan]
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iSpan = 0
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// Cut out empty buckets from start and end of spans, no matter
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// what. Also cut out empty buckets from the middle of a span but only
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// if there are more than maxEmptyBuckets consecutive empty buckets.
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for iBucket < len(buckets) {
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if nEmpty := emptyBucketsHere(); nEmpty > 0 {
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if posInSpan > 0 &&
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nEmpty < int(spans[iSpan].Length-posInSpan) &&
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nEmpty <= maxEmptyBuckets {
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// The empty buckets are in the middle of a
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// span, and there are few enough to not bother.
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// Just fast-forward.
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iBucket += nEmpty
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posInSpan += uint32(nEmpty)
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continue
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}
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// In all other cases, we cut out the empty buckets.
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buckets = append(buckets[:iBucket], buckets[iBucket+nEmpty:]...)
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if posInSpan == 0 {
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// Start of span.
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if nEmpty == int(spans[iSpan].Length) {
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// The whole span is empty.
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spans = append(spans[:iSpan], spans[iSpan+1:]...)
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continue
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}
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spans[iSpan].Length -= uint32(nEmpty)
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spans[iSpan].Offset += int32(nEmpty)
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continue
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}
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// It's in the middle or in the end of the span.
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// Split the current span.
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newSpan := Span{
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Offset: int32(nEmpty),
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Length: spans[iSpan].Length - posInSpan - uint32(nEmpty),
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}
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spans[iSpan].Length = posInSpan
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// In any case, we have to split to the next span.
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iSpan++
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posInSpan = 0
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if newSpan.Length == 0 {
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// The span is empty, so we were already at the end of a span.
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// We don't have to insert the new span, just adjust the next
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// span's offset, if there is one.
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if iSpan < len(spans) {
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spans[iSpan].Offset += int32(nEmpty)
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}
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continue
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}
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// Insert the new span.
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spans = append(spans, Span{})
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if iSpan+1 < len(spans) {
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copy(spans[iSpan+1:], spans[iSpan:])
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}
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spans[iSpan] = newSpan
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continue
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}
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iBucket++
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posInSpan++
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if posInSpan >= spans[iSpan].Length {
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posInSpan = 0
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iSpan++
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}
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}
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if maxEmptyBuckets == 0 {
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return buckets, spans
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}
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// Finally, check if any offsets between spans are small enough to merge
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// the spans.
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iBucket = int(spans[0].Length)
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iSpan = 1
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for iSpan < len(spans) {
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if int(spans[iSpan].Offset) > maxEmptyBuckets {
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iBucket += int(spans[iSpan].Length)
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iSpan++
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continue
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}
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// Merge span with previous one and insert empty buckets.
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offset := int(spans[iSpan].Offset)
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spans[iSpan-1].Length += uint32(offset) + spans[iSpan].Length
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spans = append(spans[:iSpan], spans[iSpan+1:]...)
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newBuckets := make([]float64, len(buckets)+offset)
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copy(newBuckets, buckets[:iBucket])
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copy(newBuckets[iBucket+offset:], buckets[iBucket:])
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iBucket += offset
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buckets = newBuckets
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// Note that with many merges, it would be more efficient to
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// first record all the chunks of empty buckets to insert and
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// then do it in one go through all the buckets.
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}
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return buckets, spans
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}
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// DetectReset returns true if the receiving histogram is missing any buckets
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// that have a non-zero population in the provided previous histogram. It also
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// returns true if any count (in any bucket, in the zero count, or in the count
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@ -496,7 +496,200 @@ func TestFloatHistogramCompact(t *testing.T) {
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maxEmptyBuckets int
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expected *FloatHistogram
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}{
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// TODO(beorn7): Add test cases.
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{
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"empty histogram",
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&FloatHistogram{},
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0,
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&FloatHistogram{},
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},
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{
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"nothing should happen",
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 1}, {2, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1},
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NegativeSpans: []Span{{3, 2}, {3, 2}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000},
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},
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0,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 1}, {2, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1},
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NegativeSpans: []Span{{3, 2}, {3, 2}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000},
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},
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},
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{
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"eliminate zero offsets",
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 1}, {0, 3}, {0, 1}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {0, 2}, {2, 1}, {0, 1}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4},
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},
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0,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 5}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 4}, {2, 2}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4},
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},
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},
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{
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"eliminate zero length",
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 2}, {2, 0}, {3, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {0, 0}, {2, 0}, {1, 4}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4},
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},
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0,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 2}, {5, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 4}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4},
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},
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},
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{
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"eliminate multiple zero length spans",
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 2}, {2, 0}, {2, 0}, {2, 0}, {3, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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},
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0,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 2}, {9, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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},
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},
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{
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"cut empty buckets at start or end",
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&FloatHistogram{
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PositiveSpans: []Span{{-4, 4}, {5, 3}},
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PositiveBuckets: []float64{0, 0, 1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 5}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4, 0},
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},
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0,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 2}, {5, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 4}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4},
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},
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},
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{
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"cut empty buckets at start and end",
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&FloatHistogram{
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PositiveSpans: []Span{{-4, 4}, {5, 6}},
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PositiveBuckets: []float64{0, 0, 1, 3.3, 4.2, 0.1, 3.3, 0, 0, 0},
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NegativeSpans: []Span{{-2, 4}, {3, 5}},
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NegativeBuckets: []float64{0, 0, 3.1, 3, 1.234e5, 1000, 3, 4, 0},
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},
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0,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 2}, {5, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 4}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4},
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},
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},
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{
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"cut empty buckets at start or end of chunks, even in the middle",
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&FloatHistogram{
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PositiveSpans: []Span{{-4, 6}, {3, 6}},
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PositiveBuckets: []float64{0, 0, 1, 3.3, 0, 0, 4.2, 0.1, 3.3, 0, 0, 0},
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NegativeSpans: []Span{{0, 2}, {2, 6}},
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NegativeBuckets: []float64{3.1, 3, 0, 1.234e5, 1000, 3, 4, 0},
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},
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0,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 2}, {5, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 4}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4},
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},
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},
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{
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"cut empty buckets at start or end but merge spans due to maxEmptyBuckets",
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&FloatHistogram{
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PositiveSpans: []Span{{-4, 4}, {5, 3}},
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PositiveBuckets: []float64{0, 0, 1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 5}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4, 0},
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},
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10,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 10}},
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PositiveBuckets: []float64{1, 3.3, 0, 0, 0, 0, 0, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 9}},
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NegativeBuckets: []float64{3.1, 3, 0, 0, 0, 1.234e5, 1000, 3, 4},
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},
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},
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{
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"cut empty buckets from the middle of a chunk",
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&FloatHistogram{
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PositiveSpans: []Span{{-4, 6}, {3, 3}},
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PositiveBuckets: []float64{0, 0, 1, 0, 0, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 5}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 0, 3, 4},
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},
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0,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 1}, {2, 1}, {3, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 2}, {1, 2}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 3, 4},
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},
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},
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{
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"cut empty buckets from the middle of a chunk, avoiding some due to maxEmptyBuckets",
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&FloatHistogram{
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PositiveSpans: []Span{{-4, 6}, {3, 3}},
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PositiveBuckets: []float64{0, 0, 1, 0, 0, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 5}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 0, 3, 4},
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},
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1,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 1}, {2, 1}, {3, 3}},
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PositiveBuckets: []float64{1, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 5}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 0, 3, 4},
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},
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},
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{
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"avoiding all cutting of empty buckets from the middle of a chunk due to maxEmptyBuckets",
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&FloatHistogram{
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PositiveSpans: []Span{{-4, 6}, {3, 3}},
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PositiveBuckets: []float64{0, 0, 1, 0, 0, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 5}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 0, 3, 4},
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},
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2,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 4}, {3, 3}},
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PositiveBuckets: []float64{1, 0, 0, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 5}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 0, 3, 4},
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},
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},
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{
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"everything merged into one span due to maxEmptyBuckets",
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&FloatHistogram{
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PositiveSpans: []Span{{-4, 6}, {3, 3}},
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PositiveBuckets: []float64{0, 0, 1, 0, 0, 3.3, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 2}, {3, 5}},
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NegativeBuckets: []float64{3.1, 3, 1.234e5, 1000, 0, 3, 4},
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},
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3,
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&FloatHistogram{
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PositiveSpans: []Span{{-2, 10}},
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PositiveBuckets: []float64{1, 0, 0, 3.3, 0, 0, 0, 4.2, 0.1, 3.3},
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NegativeSpans: []Span{{0, 10}},
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NegativeBuckets: []float64{3.1, 3, 0, 0, 0, 1.234e5, 1000, 0, 3, 4},
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},
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},
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}
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for _, c := range cases {
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@ -2650,16 +2650,13 @@ func TestSparseHistogramRate(t *testing.T) {
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require.Len(t, vector, 1)
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actualHistogram := vector[0].H
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expectedHistogram := &histogram.FloatHistogram{
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Schema: 1,
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ZeroThreshold: 0.001,
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ZeroCount: 1. / 15.,
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Count: 4. / 15.,
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Sum: 1.226666666666667,
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PositiveSpans: []histogram.Span{
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{Offset: 0, Length: 2},
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{Offset: 1, Length: 2},
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},
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PositiveBuckets: []float64{1. / 15., 1. / 15., 1. / 15., 1. / 15.},
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Schema: 1,
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ZeroThreshold: 0.001,
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ZeroCount: 1. / 15.,
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Count: 4. / 15.,
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Sum: 1.226666666666667,
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PositiveSpans: []histogram.Span{{Offset: 0, Length: 5}},
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PositiveBuckets: []float64{1. / 15., 1. / 15., 0, 1. / 15., 1. / 15.},
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}
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require.Equal(t, expectedHistogram, actualHistogram)
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}
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