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app/vmselect/promql: fix mode_over_time calculations

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Previously `mode_over_time` could return garbage due to improper shuffling of input data points.
This commit is contained in:
Aliaksandr Valialkin 2020-10-13 11:56:53 +03:00
parent d884ab13dc
commit f877e703c8
4 changed files with 23 additions and 4 deletions
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1
CHANGELOG.md
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@ -52,6 +52,7 @@
See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/674
* BUGFIX: vmalert: accept days, weeks and years in `for: ` part of config like Prometheus does. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/817
* BUGFIX: fix `mode_over_time(m[d])` calculations. Previously the function could return incorrect results.
# [v1.43.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.43.0)

2
app/vmselect/promql/aggr.go
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@ -494,6 +494,8 @@ func aggrFuncZScore(afa *aggrFuncArg) ([]*timeseries, error) {
//
// It is expected that a doesn't contain NaNs.
//
// The function modifies contents for a, so the caller must prepare it accordingly.
//
// See https://en.wikipedia.org/wiki/Mode_(statistics)
func modeNoNaNs(prevValue float64, a []float64) float64 {
if len(a) == 0 {

18
app/vmselect/promql/rollup.go
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@ -1587,7 +1587,23 @@ func rollupTimestamp(rfa *rollupFuncArg) float64 {
func rollupModeOverTime(rfa *rollupFuncArg) float64 {
// There is no need in handling NaNs here, since they must be cleaned up
// before calling rollup funcs.
return modeNoNaNs(rfa.prevValue, rfa.values)
// Copy rfa.values to a.A, since modeNoNaNs modifies a.A contents.
a := float64sPool.Get().(*float64s)
a.A = append(a.A[:0], rfa.values...)
result := modeNoNaNs(rfa.prevValue, a.A)
float64sPool.Put(a)
return result
}
var float64sPool = &sync.Pool{
New: func() interface{} {
return &float64s{}
},
}
type float64s struct {
A []float64
}
func rollupAscentOverTime(rfa *rollupFuncArg) float64 {

6
app/vmselect/promql/rollup_test.go
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@ -1012,7 +1012,7 @@ func TestRollupFuncsNoWindow(t *testing.T) {
}
rc.Timestamps = getTimestamps(rc.Start, rc.End, rc.Step)
values := rc.Do(nil, testValues, testTimestamps)
valuesExpected := []float64{nan, nan, 34, 44, 44}
valuesExpected := []float64{nan, 21, 34, 34, 34}
timestampsExpected := []int64{0, 40, 80, 120, 160}
testRowsEqual(t, values, rc.Timestamps, valuesExpected, timestampsExpected)
})
@ -1026,7 +1026,7 @@ func TestRollupFuncsNoWindow(t *testing.T) {
}
rc.Timestamps = getTimestamps(rc.Start, rc.End, rc.Step)
values := rc.Do(nil, testValues, testTimestamps)
valuesExpected := []float64{nan, 1262.5, 3187.5, 4059.523809523809, 6200}
valuesExpected := []float64{nan, 2775, 5262.5, 3678.5714285714284, 2880}
timestampsExpected := []int64{0, 40, 80, 120, 160}
testRowsEqual(t, values, rc.Timestamps, valuesExpected, timestampsExpected)
})
@ -1040,7 +1040,7 @@ func TestRollupFuncsNoWindow(t *testing.T) {
}
rc.Timestamps = getTimestamps(rc.Start, rc.End, rc.Step)
values := rc.Do(nil, testValues, testTimestamps)
valuesExpected := []float64{nan, 0.9397878236968458, 1.1969836716333457, 2.3112921116373175, nan}
valuesExpected := []float64{nan, -0.86650328627136, -1.1200838283548589, -0.40035755084856683, nan}
timestampsExpected := []int64{0, 40, 80, 120, 160}
testRowsEqual(t, values, rc.Timestamps, valuesExpected, timestampsExpected)
})