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prometheus/model/histogram/histogram_test.go
beorn7 a7c519930e histograms: Add Compact method to the normal integer Histogram 
And use the new method to call to compact Histograms during
parsing. This happens for both `Histogram` and `FloatHistogram`. In
this way, if targets decide to optimize the exposition size by merging
spans with empty buckets in between, we still get a normalized
results. It will also normalize away any valid but weird
representations like empty spans, spans with offset zero, and empty
buckets at the start or end of a span.

The implementation seemed easy at first as it just turns the
`compactBuckets` helper into a generic function (which now got its own
file). However, the integer Histograms have delta buckets instead of
absolute buckets, which had to be treated specially in the generic
`compactBuckets` function. To make sure it works, I have added plenty
of explicit tests for `Histogram` in addition to the `FloatHistogram`
tests.

I have also updated the doc comment for the `Compact` method.

Based on the insights now expressed in the doc comment, compacting
with a maxEmptyBuckets > 0 is rarely useful. Therefore, this commit
also sets the value to 0 in the two cases we were using 3 so far. We
might still want to reconsider, so I don't want to remove the
maxEmptyBuckets parameter right now.

Signed-off-by: beorn7 <beorn@grafana.com>
2022-09-27 13:04:16 +02:00

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// Copyright 2021 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package histogram
import (
"fmt"
"math"
"testing"
"github.com/stretchr/testify/require"
)
func TestHistogramString(t *testing.T) {
cases := []struct {
histogram Histogram
expectedString string
}{
{
histogram: Histogram{
Schema: 0,
},
expectedString: "{count:0, sum:0}",
},
{
histogram: Histogram{
Schema: 0,
Count: 9,
Sum: -3.1415,
ZeroCount: 12,
ZeroThreshold: 0.001,
NegativeSpans: []Span{
{Offset: 0, Length: 5},
{Offset: 1, Length: 1},
},
NegativeBuckets: []int64{1, 2, -2, 1, -1, 0},
},
expectedString: "{count:9, sum:-3.1415, [-64,-32):1, [-16,-8):1, [-8,-4):2, [-4,-2):1, [-2,-1):3, [-1,-0.5):1, [-0.001,0.001]:12}",
},
{
histogram: Histogram{
Schema: 0,
Count: 19,
Sum: 2.7,
PositiveSpans: []Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 0},
NegativeSpans: []Span{
{Offset: 0, Length: 5},
{Offset: 1, Length: 0},
{Offset: 0, Length: 1},
},
NegativeBuckets: []int64{1, 2, -2, 1, -1, 0},
},
expectedString: "{count:19, sum:2.7, [-64,-32):1, [-16,-8):1, [-8,-4):2, [-4,-2):1, [-2,-1):3, [-1,-0.5):1, (0.5,1]:1, (1,2]:3, (2,4]:1, (4,8]:2, (8,16]:1, (16,32]:1, (32,64]:1}",
},
}
for i, c := range cases {
t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
actualString := c.histogram.String()
require.Equal(t, c.expectedString, actualString)
})
}
}
func TestCumulativeBucketIterator(t *testing.T) {
cases := []struct {
histogram Histogram
expectedBuckets []Bucket
}{
{
histogram: Histogram{
Schema: 0,
PositiveSpans: []Span{
{Offset: 0, Length: 2},
{Offset: 1, Length: 2},
},
PositiveBuckets: []int64{1, 1, -1, 0},
},
expectedBuckets: []Bucket{
{Lower: math.Inf(-1), Upper: 1, Count: 1, LowerInclusive: true, UpperInclusive: true, Index: 0},
{Lower: math.Inf(-1), Upper: 2, Count: 3, LowerInclusive: true, UpperInclusive: true, Index: 1},
{Lower: math.Inf(-1), Upper: 4, Count: 3, LowerInclusive: true, UpperInclusive: true, Index: 2},
{Lower: math.Inf(-1), Upper: 8, Count: 4, LowerInclusive: true, UpperInclusive: true, Index: 3},
{Lower: math.Inf(-1), Upper: 16, Count: 5, LowerInclusive: true, UpperInclusive: true, Index: 4},
},
},
{
histogram: Histogram{
Schema: 0,
PositiveSpans: []Span{
{Offset: 0, Length: 5},
{Offset: 1, Length: 1},
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0},
},
expectedBuckets: []Bucket{
{Lower: math.Inf(-1), Upper: 1, Count: 1, LowerInclusive: true, UpperInclusive: true, Index: 0},
{Lower: math.Inf(-1), Upper: 2, Count: 4, LowerInclusive: true, UpperInclusive: true, Index: 1},
{Lower: math.Inf(-1), Upper: 4, Count: 5, LowerInclusive: true, UpperInclusive: true, Index: 2},
{Lower: math.Inf(-1), Upper: 8, Count: 7, LowerInclusive: true, UpperInclusive: true, Index: 3},
{Lower: math.Inf(-1), Upper: 16, Count: 8, LowerInclusive: true, UpperInclusive: true, Index: 4},
{Lower: math.Inf(-1), Upper: 32, Count: 8, LowerInclusive: true, UpperInclusive: true, Index: 5},
{Lower: math.Inf(-1), Upper: 64, Count: 9, LowerInclusive: true, UpperInclusive: true, Index: 6},
},
},
{
histogram: Histogram{
Schema: 0,
PositiveSpans: []Span{
{Offset: 0, Length: 7},
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 0},
},
expectedBuckets: []Bucket{
{Lower: math.Inf(-1), Upper: 1, Count: 1, LowerInclusive: true, UpperInclusive: true, Index: 0},
{Lower: math.Inf(-1), Upper: 2, Count: 4, LowerInclusive: true, UpperInclusive: true, Index: 1},
{Lower: math.Inf(-1), Upper: 4, Count: 5, LowerInclusive: true, UpperInclusive: true, Index: 2},
{Lower: math.Inf(-1), Upper: 8, Count: 7, LowerInclusive: true, UpperInclusive: true, Index: 3},
{Lower: math.Inf(-1), Upper: 16, Count: 8, LowerInclusive: true, UpperInclusive: true, Index: 4},
{Lower: math.Inf(-1), Upper: 32, Count: 9, LowerInclusive: true, UpperInclusive: true, Index: 5},
{Lower: math.Inf(-1), Upper: 64, Count: 10, LowerInclusive: true, UpperInclusive: true, Index: 6},
},
},
{
histogram: Histogram{
Schema: 3,
PositiveSpans: []Span{
{Offset: -5, Length: 2}, // -5 -4
{Offset: 2, Length: 3}, // -1 0 1
{Offset: 2, Length: 2}, // 4 5
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 3},
},
expectedBuckets: []Bucket{
{Lower: math.Inf(-1), Upper: 0.6484197773255048, Count: 1, LowerInclusive: true, UpperInclusive: true, Index: -5},
{Lower: math.Inf(-1), Upper: 0.7071067811865475, Count: 4, LowerInclusive: true, UpperInclusive: true, Index: -4},
{Lower: math.Inf(-1), Upper: 0.7711054127039704, Count: 4, LowerInclusive: true, UpperInclusive: true, Index: -3},
{Lower: math.Inf(-1), Upper: 0.8408964152537144, Count: 4, LowerInclusive: true, UpperInclusive: true, Index: -2},
{Lower: math.Inf(-1), Upper: 0.9170040432046711, Count: 5, LowerInclusive: true, UpperInclusive: true, Index: -1},
{Lower: math.Inf(-1), Upper: 1, Count: 7, LowerInclusive: true, UpperInclusive: true, Index: 0},
{Lower: math.Inf(-1), Upper: 1.0905077326652577, Count: 8, LowerInclusive: true, UpperInclusive: true, Index: 1},
{Lower: math.Inf(-1), Upper: 1.189207115002721, Count: 8, LowerInclusive: true, UpperInclusive: true, Index: 2},
{Lower: math.Inf(-1), Upper: 1.2968395546510096, Count: 8, LowerInclusive: true, UpperInclusive: true, Index: 3},
{Lower: math.Inf(-1), Upper: 1.414213562373095, Count: 9, LowerInclusive: true, UpperInclusive: true, Index: 4},
{Lower: math.Inf(-1), Upper: 1.5422108254079407, Count: 13, LowerInclusive: true, UpperInclusive: true, Index: 5},
},
},
{
histogram: Histogram{
Schema: -2,
PositiveSpans: []Span{
{Offset: -2, Length: 4}, // -2 -1 0 1
{Offset: 2, Length: 2}, // 4 5
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0},
},
expectedBuckets: []Bucket{
{Lower: math.Inf(-1), Upper: 0.00390625, Count: 1, LowerInclusive: true, UpperInclusive: true, Index: -2},
{Lower: math.Inf(-1), Upper: 0.0625, Count: 4, LowerInclusive: true, UpperInclusive: true, Index: -1},
{Lower: math.Inf(-1), Upper: 1, Count: 5, LowerInclusive: true, UpperInclusive: true, Index: 0},
{Lower: math.Inf(-1), Upper: 16, Count: 7, LowerInclusive: true, UpperInclusive: true, Index: 1},
{Lower: math.Inf(-1), Upper: 256, Count: 7, LowerInclusive: true, UpperInclusive: true, Index: 2},
{Lower: math.Inf(-1), Upper: 4096, Count: 7, LowerInclusive: true, UpperInclusive: true, Index: 3},
{Lower: math.Inf(-1), Upper: 65536, Count: 8, LowerInclusive: true, UpperInclusive: true, Index: 4},
{Lower: math.Inf(-1), Upper: 1048576, Count: 9, LowerInclusive: true, UpperInclusive: true, Index: 5},
},
},
{
histogram: Histogram{
Schema: -1,
PositiveSpans: []Span{
{Offset: -2, Length: 5}, // -2 -1 0 1 2
},
PositiveBuckets: []int64{1, 2, -2, 1, -1},
},
expectedBuckets: []Bucket{
{Lower: math.Inf(-1), Upper: 0.0625, Count: 1, LowerInclusive: true, UpperInclusive: true, Index: -2},
{Lower: math.Inf(-1), Upper: 0.25, Count: 4, LowerInclusive: true, UpperInclusive: true, Index: -1},
{Lower: math.Inf(-1), Upper: 1, Count: 5, LowerInclusive: true, UpperInclusive: true, Index: 0},
{Lower: math.Inf(-1), Upper: 4, Count: 7, LowerInclusive: true, UpperInclusive: true, Index: 1},
{Lower: math.Inf(-1), Upper: 16, Count: 8, LowerInclusive: true, UpperInclusive: true, Index: 2},
},
},
}
for i, c := range cases {
t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
it := c.histogram.CumulativeBucketIterator()
actualBuckets := make([]Bucket, 0, len(c.expectedBuckets))
for it.Next() {
actualBuckets = append(actualBuckets, it.At())
}
require.Equal(t, c.expectedBuckets, actualBuckets)
})
}
}
func TestRegularBucketIterator(t *testing.T) {
cases := []struct {
histogram Histogram
expectedPositiveBuckets []Bucket
expectedNegativeBuckets []Bucket
}{
{
histogram: Histogram{
Schema: 0,
},
expectedPositiveBuckets: []Bucket{},
expectedNegativeBuckets: []Bucket{},
},
{
histogram: Histogram{
Schema: 0,
PositiveSpans: []Span{
{Offset: 0, Length: 2},
{Offset: 1, Length: 2},
},
PositiveBuckets: []int64{1, 1, -1, 0},
},
expectedPositiveBuckets: []Bucket{
{Lower: 0.5, Upper: 1, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 0},
{Lower: 1, Upper: 2, Count: 2, LowerInclusive: false, UpperInclusive: true, Index: 1},
{Lower: 4, Upper: 8, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 3},
{Lower: 8, Upper: 16, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 4},
},
expectedNegativeBuckets: []Bucket{},
},
{
histogram: Histogram{
Schema: 0,
NegativeSpans: []Span{
{Offset: 0, Length: 5},
{Offset: 1, Length: 1},
},
NegativeBuckets: []int64{1, 2, -2, 1, -1, 0},
},
expectedPositiveBuckets: []Bucket{},
expectedNegativeBuckets: []Bucket{
{Lower: -1, Upper: -0.5, Count: 1, LowerInclusive: true, UpperInclusive: false, Index: 0},
{Lower: -2, Upper: -1, Count: 3, LowerInclusive: true, UpperInclusive: false, Index: 1},
{Lower: -4, Upper: -2, Count: 1, LowerInclusive: true, UpperInclusive: false, Index: 2},
{Lower: -8, Upper: -4, Count: 2, LowerInclusive: true, UpperInclusive: false, Index: 3},
{Lower: -16, Upper: -8, Count: 1, LowerInclusive: true, UpperInclusive: false, Index: 4},
{Lower: -64, Upper: -32, Count: 1, LowerInclusive: true, UpperInclusive: false, Index: 6},
},
},
{
histogram: Histogram{
Schema: 0,
PositiveSpans: []Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 0},
NegativeSpans: []Span{
{Offset: 0, Length: 5},
{Offset: 1, Length: 0},
{Offset: 0, Length: 1},
},
NegativeBuckets: []int64{1, 2, -2, 1, -1, 0},
},
expectedPositiveBuckets: []Bucket{
{Lower: 0.5, Upper: 1, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 0},
{Lower: 1, Upper: 2, Count: 3, LowerInclusive: false, UpperInclusive: true, Index: 1},
{Lower: 2, Upper: 4, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 2},
{Lower: 4, Upper: 8, Count: 2, LowerInclusive: false, UpperInclusive: true, Index: 3},
{Lower: 8, Upper: 16, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 4},
{Lower: 16, Upper: 32, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 5},
{Lower: 32, Upper: 64, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 6},
},
expectedNegativeBuckets: []Bucket{
{Lower: -1, Upper: -0.5, Count: 1, LowerInclusive: true, UpperInclusive: false, Index: 0},
{Lower: -2, Upper: -1, Count: 3, LowerInclusive: true, UpperInclusive: false, Index: 1},
{Lower: -4, Upper: -2, Count: 1, LowerInclusive: true, UpperInclusive: false, Index: 2},
{Lower: -8, Upper: -4, Count: 2, LowerInclusive: true, UpperInclusive: false, Index: 3},
{Lower: -16, Upper: -8, Count: 1, LowerInclusive: true, UpperInclusive: false, Index: 4},
{Lower: -64, Upper: -32, Count: 1, LowerInclusive: true, UpperInclusive: false, Index: 6},
},
},
{
histogram: Histogram{
Schema: 3,
PositiveSpans: []Span{
{Offset: -5, Length: 2}, // -5 -4
{Offset: 2, Length: 3}, // -1 0 1
{Offset: 2, Length: 2}, // 4 5
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 3},
},
expectedPositiveBuckets: []Bucket{
{Lower: 0.5946035575013605, Upper: 0.6484197773255048, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: -5},
{Lower: 0.6484197773255048, Upper: 0.7071067811865475, Count: 3, LowerInclusive: false, UpperInclusive: true, Index: -4},
{Lower: 0.8408964152537144, Upper: 0.9170040432046711, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: -1},
{Lower: 0.9170040432046711, Upper: 1, Count: 2, LowerInclusive: false, UpperInclusive: true, Index: 0},
{Lower: 1, Upper: 1.0905077326652577, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 1},
{Lower: 1.2968395546510096, Upper: 1.414213562373095, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 4},
{Lower: 1.414213562373095, Upper: 1.5422108254079407, Count: 4, LowerInclusive: false, UpperInclusive: true, Index: 5},
},
expectedNegativeBuckets: []Bucket{},
},
{
histogram: Histogram{
Schema: -2,
PositiveSpans: []Span{
{Offset: -2, Length: 4}, // -2 -1 0 1
{Offset: 2, Length: 2}, // 4 5
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0},
},
expectedPositiveBuckets: []Bucket{
{Lower: 0.000244140625, Upper: 0.00390625, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: -2},
{Lower: 0.00390625, Upper: 0.0625, Count: 3, LowerInclusive: false, UpperInclusive: true, Index: -1},
{Lower: 0.0625, Upper: 1, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 0},
{Lower: 1, Upper: 16, Count: 2, LowerInclusive: false, UpperInclusive: true, Index: 1},
{Lower: 4096, Upper: 65536, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 4},
{Lower: 65536, Upper: 1048576, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 5},
},
expectedNegativeBuckets: []Bucket{},
},
{
histogram: Histogram{
Schema: -1,
PositiveSpans: []Span{
{Offset: -2, Length: 5}, // -2 -1 0 1 2
},
PositiveBuckets: []int64{1, 2, -2, 1, -1},
},
expectedPositiveBuckets: []Bucket{
{Lower: 0.015625, Upper: 0.0625, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: -2},
{Lower: 0.0625, Upper: 0.25, Count: 3, LowerInclusive: false, UpperInclusive: true, Index: -1},
{Lower: 0.25, Upper: 1, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 0},
{Lower: 1, Upper: 4, Count: 2, LowerInclusive: false, UpperInclusive: true, Index: 1},
{Lower: 4, Upper: 16, Count: 1, LowerInclusive: false, UpperInclusive: true, Index: 2},
},
expectedNegativeBuckets: []Bucket{},
},
}
for i, c := range cases {
t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
it := c.histogram.PositiveBucketIterator()
actualPositiveBuckets := make([]Bucket, 0, len(c.expectedPositiveBuckets))
for it.Next() {
actualPositiveBuckets = append(actualPositiveBuckets, it.At())
}
require.Equal(t, c.expectedPositiveBuckets, actualPositiveBuckets)
it = c.histogram.NegativeBucketIterator()
actualNegativeBuckets := make([]Bucket, 0, len(c.expectedNegativeBuckets))
for it.Next() {
actualNegativeBuckets = append(actualNegativeBuckets, it.At())
}
require.Equal(t, c.expectedNegativeBuckets, actualNegativeBuckets)
})
}
}
func TestHistogramToFloat(t *testing.T) {
h := Histogram{
Schema: 3,
Count: 61,
Sum: 2.7,
ZeroThreshold: 0.1,
ZeroCount: 42,
PositiveSpans: []Span{
{Offset: 0, Length: 4},
{Offset: 0, Length: 0},
{Offset: 0, Length: 3},
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 0},
NegativeSpans: []Span{
{Offset: 0, Length: 5},
{Offset: 1, Length: 0},
{Offset: 0, Length: 1},
},
NegativeBuckets: []int64{1, 2, -2, 1, -1, 0},
}
fh := h.ToFloat()
require.Equal(t, h.String(), fh.String())
}
func TestHistogramMatches(t *testing.T) {
h1 := Histogram{
Schema: 3,
Count: 61,
Sum: 2.7,
ZeroThreshold: 0.1,
ZeroCount: 42,
PositiveSpans: []Span{
{Offset: 0, Length: 4},
{Offset: 10, Length: 3},
},
PositiveBuckets: []int64{1, 2, -2, 1, -1, 0, 0},
NegativeSpans: []Span{
{Offset: 0, Length: 4},
{Offset: 10, Length: 3},
},
NegativeBuckets: []int64{1, 2, -2, 1, -1, 0, 0},
}
h2 := h1.Copy()
require.True(t, h1.Equals(h2))
// Changed spans but same layout.
h2.PositiveSpans = append(h2.PositiveSpans, Span{Offset: 5})
h2.NegativeSpans = append(h2.NegativeSpans, Span{Offset: 2})
require.True(t, h1.Equals(h2))
require.True(t, h2.Equals(&h1))
// Adding empty spans in between.
h2.PositiveSpans[1].Offset = 6
h2.PositiveSpans = []Span{
h2.PositiveSpans[0],
{Offset: 1},
{Offset: 3},
h2.PositiveSpans[1],
h2.PositiveSpans[2],
}
h2.NegativeSpans[1].Offset = 5
h2.NegativeSpans = []Span{
h2.NegativeSpans[0],
{Offset: 2},
{Offset: 3},
h2.NegativeSpans[1],
h2.NegativeSpans[2],
}
require.True(t, h1.Equals(h2))
require.True(t, h2.Equals(&h1))
// All mismatches.
require.False(t, h1.Equals(nil))
h2.Schema = 1
require.False(t, h1.Equals(h2))
h2 = h1.Copy()
h2.Count++
require.False(t, h1.Equals(h2))
h2 = h1.Copy()
h2.Sum++
require.False(t, h1.Equals(h2))
h2 = h1.Copy()
h2.ZeroThreshold++
require.False(t, h1.Equals(h2))
h2 = h1.Copy()
h2.ZeroCount++
require.False(t, h1.Equals(h2))
// Changing value of buckets.
h2 = h1.Copy()
h2.PositiveBuckets[len(h2.PositiveBuckets)-1]++
require.False(t, h1.Equals(h2))
h2 = h1.Copy()
h2.NegativeBuckets[len(h2.NegativeBuckets)-1]++
require.False(t, h1.Equals(h2))
// Changing bucket layout.
h2 = h1.Copy()
h2.PositiveSpans[1].Offset++
require.False(t, h1.Equals(h2))
h2 = h1.Copy()
h2.NegativeSpans[1].Offset++
require.False(t, h1.Equals(h2))
// Adding an empty bucket.
h2 = h1.Copy()
h2.PositiveSpans[0].Offset--
h2.PositiveSpans[0].Length++
h2.PositiveBuckets = append([]int64{0}, h2.PositiveBuckets...)
require.False(t, h1.Equals(h2))
h2 = h1.Copy()
h2.NegativeSpans[0].Offset--
h2.NegativeSpans[0].Length++
h2.NegativeBuckets = append([]int64{0}, h2.NegativeBuckets...)
require.False(t, h1.Equals(h2))
// Adding new bucket.
h2 = h1.Copy()
h2.PositiveSpans = append(h2.PositiveSpans, Span{
Offset: 1,
Length: 1,
})
h2.PositiveBuckets = append(h2.PositiveBuckets, 1)
require.False(t, h1.Equals(h2))
h2 = h1.Copy()
h2.NegativeSpans = append(h2.NegativeSpans, Span{
Offset: 1,
Length: 1,
})
h2.NegativeBuckets = append(h2.NegativeBuckets, 1)
require.False(t, h1.Equals(h2))
}
func TestHistogramCompact(t *testing.T) {
cases := []struct {
name string
in *Histogram
maxEmptyBuckets int
expected *Histogram
}{
{
"empty histogram",
&Histogram{},
0,
&Histogram{},
},
{
"nothing should happen",
&Histogram{
PositiveSpans: []Span{{-2, 1}, {2, 3}},
PositiveBuckets: []int64{1, 3, -3, 42},
NegativeSpans: []Span{{3, 2}, {3, 2}},
NegativeBuckets: []int64{5, 3, 1.234e5, 1000},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 1}, {2, 3}},
PositiveBuckets: []int64{1, 3, -3, 42},
NegativeSpans: []Span{{3, 2}, {3, 2}},
NegativeBuckets: []int64{5, 3, 1.234e5, 1000},
},
},
{
"eliminate zero offsets",
&Histogram{
PositiveSpans: []Span{{-2, 1}, {0, 3}, {0, 1}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 2}, {0, 2}, {2, 1}, {0, 1}},
NegativeBuckets: []int64{5, 3, 1.234e5, 1000, 3, 4},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 5}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 4}, {2, 2}},
NegativeBuckets: []int64{5, 3, 1.234e5, 1000, 3, 4},
},
},
{
"eliminate zero length",
&Histogram{
PositiveSpans: []Span{{-2, 2}, {2, 0}, {3, 3}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 2}, {0, 0}, {2, 0}, {1, 4}},
NegativeBuckets: []int64{5, 3, 1.234e5, 1000, 3, 4},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 2}, {5, 3}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 4}},
NegativeBuckets: []int64{5, 3, 1.234e5, 1000, 3, 4},
},
},
{
"eliminate multiple zero length spans",
&Histogram{
PositiveSpans: []Span{{-2, 2}, {2, 0}, {2, 0}, {2, 0}, {3, 3}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 2}, {9, 3}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
},
},
{
"cut empty buckets at start or end",
&Histogram{
PositiveSpans: []Span{{-4, 4}, {5, 3}},
PositiveBuckets: []int64{0, 0, 1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 5}},
NegativeBuckets: []int64{5, 3, -4, -2, 3, 4, -9},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 2}, {5, 3}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 4}},
NegativeBuckets: []int64{5, 3, -4, -2, 3, 4},
},
},
{
"cut empty buckets at start and end",
&Histogram{
PositiveSpans: []Span{{-4, 4}, {5, 6}},
PositiveBuckets: []int64{0, 0, 1, 3, -3, 42, 3, -46, 0, 0},
NegativeSpans: []Span{{-2, 4}, {3, 5}},
NegativeBuckets: []int64{0, 0, 5, 3, -4, -2, 3, 4, -9},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 2}, {5, 3}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 4}},
NegativeBuckets: []int64{5, 3, -4, -2, 3, 4},
},
},
{
"cut empty buckets at start or end of spans, even in the middle",
&Histogram{
PositiveSpans: []Span{{-4, 6}, {3, 6}},
PositiveBuckets: []int64{0, 0, 1, 3, -4, 0, 1, 42, 3, -46, 0, 0},
NegativeSpans: []Span{{0, 2}, {2, 6}},
NegativeBuckets: []int64{5, 3, -8, 4, -2, 3, 4, -9},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 2}, {5, 3}},
PositiveBuckets: []int64{1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 4}},
NegativeBuckets: []int64{5, 3, -4, -2, 3, 4},
},
},
{
"cut empty buckets at start or end but merge spans due to maxEmptyBuckets",
&Histogram{
PositiveSpans: []Span{{-4, 4}, {5, 3}},
PositiveBuckets: []int64{0, 0, 1, 3, -3, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 5}},
NegativeBuckets: []int64{5, 3, -4, -2, 3, 4, -9},
},
10,
&Histogram{
PositiveSpans: []Span{{-2, 10}},
PositiveBuckets: []int64{1, 3, -4, 0, 0, 0, 0, 1, 42, 3},
NegativeSpans: []Span{{0, 9}},
NegativeBuckets: []int64{5, 3, -8, 0, 0, 4, -2, 3, 4},
},
},
{
"cut empty buckets from the middle of a span",
&Histogram{
PositiveSpans: []Span{{-4, 6}, {3, 3}},
PositiveBuckets: []int64{0, 0, 1, -1, 0, 3, -2, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 5}},
NegativeBuckets: []int64{5, 3, -4, -2, -2, 3, 4},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 1}, {2, 1}, {3, 3}},
PositiveBuckets: []int64{1, 2, -2, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 2}, {1, 2}},
NegativeBuckets: []int64{5, 3, -4, -2, 1, 4},
},
},
{
"cut out a span containing only empty buckets",
&Histogram{
PositiveSpans: []Span{{-4, 3}, {2, 2}, {3, 4}},
PositiveBuckets: []int64{0, 0, 1, -1, 0, 3, -2, 42, 3},
},
0,
&Histogram{
PositiveSpans: []Span{{-2, 1}, {7, 4}},
PositiveBuckets: []int64{1, 2, -2, 42, 3},
},
},
{
"cut empty buckets from the middle of a span, avoiding some due to maxEmptyBuckets",
&Histogram{
PositiveSpans: []Span{{-4, 6}, {3, 3}},
PositiveBuckets: []int64{0, 0, 1, -1, 0, 3, -2, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 5}},
NegativeBuckets: []int64{5, 3, -4, -2, -2, 3, 4},
},
1,
&Histogram{
PositiveSpans: []Span{{-2, 1}, {2, 1}, {3, 3}},
PositiveBuckets: []int64{1, 2, -2, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 5}},
NegativeBuckets: []int64{5, 3, -4, -2, -2, 3, 4},
},
},
{
"avoiding all cutting of empty buckets from the middle of a chunk due to maxEmptyBuckets",
&Histogram{
PositiveSpans: []Span{{-4, 6}, {3, 3}},
PositiveBuckets: []int64{0, 0, 1, -1, 0, 3, -2, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 5}},
NegativeBuckets: []int64{5, 3, -4, -2, -2, 3, 4},
},
2,
&Histogram{
PositiveSpans: []Span{{-2, 4}, {3, 3}},
PositiveBuckets: []int64{1, -1, 0, 3, -2, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 5}},
NegativeBuckets: []int64{5, 3, -4, -2, -2, 3, 4},
},
},
{
"everything merged into one span due to maxEmptyBuckets",
&Histogram{
PositiveSpans: []Span{{-4, 6}, {3, 3}},
PositiveBuckets: []int64{0, 0, 1, -1, 0, 3, -2, 42, 3},
NegativeSpans: []Span{{0, 2}, {3, 5}},
NegativeBuckets: []int64{5, 3, -4, -2, -2, 3, 4},
},
3,
&Histogram{
PositiveSpans: []Span{{-2, 10}},
PositiveBuckets: []int64{1, -1, 0, 3, -3, 0, 0, 1, 42, 3},
NegativeSpans: []Span{{0, 10}},
NegativeBuckets: []int64{5, 3, -8, 0, 0, 4, -2, -2, 3, 4},
},
},
{
"only empty buckets and maxEmptyBuckets greater zero",
&Histogram{
PositiveSpans: []Span{{-4, 6}, {3, 3}},
PositiveBuckets: []int64{0, 0, 0, 0, 0, 0, 0, 0, 0},
NegativeSpans: []Span{{0, 7}},
NegativeBuckets: []int64{0, 0, 0, 0, 0, 0, 0},
},
3,
&Histogram{
PositiveSpans: []Span{},
PositiveBuckets: []int64{},
NegativeSpans: []Span{},
NegativeBuckets: []int64{},
},
},
{
"multiple spans of only empty buckets",
&Histogram{
PositiveSpans: []Span{{-10, 2}, {2, 1}, {3, 3}},
PositiveBuckets: []int64{0, 0, 0, 0, 2, 3},
NegativeSpans: []Span{{-10, 2}, {2, 1}, {3, 3}},
NegativeBuckets: []int64{2, 3, -5, 0, 0, 0},
},
0,
&Histogram{
PositiveSpans: []Span{{-1, 2}},
PositiveBuckets: []int64{2, 3},
NegativeSpans: []Span{{-10, 2}},
NegativeBuckets: []int64{2, 3},
},
},
}
for _, c := range cases {
t.Run(c.name, func(t *testing.T) {
require.Equal(t, c.expected, c.in.Compact(c.maxEmptyBuckets))
// Compact has happened in-place, too.
require.Equal(t, c.expected, c.in)
})
}
}
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