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Histogram: Fix allFloatBucketIterator

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If the zero threshold overlaps with the highest negative bucket and/or
the lowest positive bucket, its upper or lower boundary, respectively,
has to be adjusted. In valid histograms, only ever the highest
negative bucket and/or the lowest positive bucket may overlap with the
zero bucket. This is assumed in this code to simplify the checks.

Signed-off-by: beorn7 <beorn@grafana.com>
This commit is contained in:
beorn7 2022-05-03 16:24:11 +02:00
parent bcc919cb19
commit 2d233cf95e
2 changed files with 79 additions and 3 deletions
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10
model/histogram/float_histogram.go
View file

@ -655,7 +655,9 @@ func (h *FloatHistogram) NegativeReverseBucketIterator() FloatBucketIterator {
// AllBucketIterator returns a FloatBucketIterator to iterate over all negative,
// zero, and positive buckets in ascending order (starting at the lowest bucket
// and going up).
// and going up). If the highest negative bucket or the lowest positive bucket
// overlap with the zero bucket, their upper or lower boundary, respectively, is
// set to the zero threshold.
func (h *FloatHistogram) AllBucketIterator() FloatBucketIterator {
return &allFloatBucketIterator{
h: h,
@ -1071,6 +1073,9 @@ func (r *allFloatBucketIterator) Next() bool {
case -1:
if r.negIter.Next() {
r.currBucket = r.negIter.At()
if r.currBucket.Upper > -r.h.ZeroThreshold {
r.currBucket.Upper = -r.h.ZeroThreshold
}
return true
}
r.state = 0
@ -1092,6 +1097,9 @@ func (r *allFloatBucketIterator) Next() bool {
case 1:
if r.posIter.Next() {
r.currBucket = r.posIter.At()
if r.currBucket.Lower < r.h.ZeroThreshold {
r.currBucket.Lower = r.h.ZeroThreshold
}
return true
}
r.state = 42

72
model/histogram/float_histogram_test.go
View file

@ -1729,6 +1729,66 @@ func TestAllFloatBucketIterator(t *testing.T) {
includeZero: false,
includePos: true,
},
{
h: FloatHistogram{
Count: 447,
ZeroCount: 42,
ZeroThreshold: 0.5, // Coinciding with bucket boundary.
Sum: 1008.4,
Schema: 0,
PositiveSpans: []Span{
{Offset: 0, Length: 4},
{Offset: 1, Length: 0},
{Offset: 3, Length: 3},
{Offset: 3, Length: 0},
{Offset: 2, Length: 0},
{Offset: 5, Length: 3},
},
PositiveBuckets: []float64{100, 344, 123, 55, 3, 63, 2, 54, 235, 33},
NegativeSpans: []Span{
{Offset: 0, Length: 3},
{Offset: 1, Length: 0},
{Offset: 3, Length: 0},
{Offset: 3, Length: 4},
{Offset: 2, Length: 0},
{Offset: 5, Length: 3},
},
NegativeBuckets: []float64{10, 34, 1230, 54, 67, 63, 2, 554, 235, 33},
},
includeNeg: true,
includeZero: true,
includePos: true,
},
{
h: FloatHistogram{
Count: 447,
ZeroCount: 42,
ZeroThreshold: 0.6, // Within the bucket closest to zero.
Sum: 1008.4,
Schema: 0,
PositiveSpans: []Span{
{Offset: 0, Length: 4},
{Offset: 1, Length: 0},
{Offset: 3, Length: 3},
{Offset: 3, Length: 0},
{Offset: 2, Length: 0},
{Offset: 5, Length: 3},
},
PositiveBuckets: []float64{100, 344, 123, 55, 3, 63, 2, 54, 235, 33},
NegativeSpans: []Span{
{Offset: 0, Length: 3},
{Offset: 1, Length: 0},
{Offset: 3, Length: 0},
{Offset: 3, Length: 4},
{Offset: 2, Length: 0},
{Offset: 5, Length: 3},
},
NegativeBuckets: []float64{10, 34, 1230, 54, 67, 63, 2, 554, 235, 33},
},
includeNeg: true,
includeZero: true,
includePos: true,
},
}
for i, c := range cases {
@ -1738,7 +1798,11 @@ func TestAllFloatBucketIterator(t *testing.T) {
if c.includeNeg {
it := c.h.NegativeReverseBucketIterator()
for it.Next() {
expBuckets = append(expBuckets, it.At())
b := it.At()
if c.includeZero && b.Upper > -c.h.ZeroThreshold {
b.Upper = -c.h.ZeroThreshold
}
expBuckets = append(expBuckets, b)
}
}
if c.includeZero {
@ -1753,7 +1817,11 @@ func TestAllFloatBucketIterator(t *testing.T) {
if c.includePos {
it := c.h.PositiveBucketIterator()
for it.Next() {
expBuckets = append(expBuckets, it.At())
b := it.At()
if c.includeZero && b.Lower < c.h.ZeroThreshold {
b.Lower = c.h.ZeroThreshold
}
expBuckets = append(expBuckets, b)
}
}