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promql: fix smoothSeries() @ modifier timestamp mismatch

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smoothSeries() was stamping output points at offset-adjusted timestamps
instead of evaluator timestamps. When the @ modifier is used, this
causes gatherVector() to miss the points because it matches by exact
timestamp equality against evaluator step timestamps.

Fix by iterating over evaluator timestamps and deriving data timestamps
by subtracting the offset, so output points align with what
gatherVector() expects.

Signed-off-by: Julien Pivotto <291750+roidelapluie@users.noreply.github.com>
This commit is contained in:
Julien Pivotto 2026-04-16 13:40:48 +02:00
parent 25d678b502
commit 85dbc3cc76
2 changed files with 21 additions and 13 deletions
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26
promql/engine.go
View File

@ -1712,8 +1712,6 @@ func (ev *evaluator) smoothSeries(series []storage.Series, offset time.Duration)
it := storage.NewBuffer(dur + 2*durationMilliseconds(ev.lookbackDelta))
offMS := offset.Milliseconds()
start := ev.startTimestamp - offMS
end := ev.endTimestamp - offMS
step := ev.interval
lb := durationMilliseconds(ev.lookbackDelta)
@ -1729,9 +1727,11 @@ func (ev *evaluator) smoothSeries(series []storage.Series, offset time.Duration)
var floats []FPoint
var hists []HPoint
for ts := start; ts <= end; ts += step {
matrixStart := ts - lb
matrixEnd := ts + lb
for evalTS := ev.startTimestamp; evalTS <= ev.endTimestamp; evalTS += step {
// Apply offset to get the data timestamp.
dataTS := evalTS - offMS
matrixStart := dataTS - lb
matrixEnd := dataTS + lb
floats, hists = ev.matrixIterSlice(it, matrixStart, matrixEnd, floats, hists)
if len(floats) == 0 && len(hists) == 0 {
@ -1743,28 +1743,28 @@ func (ev *evaluator) smoothSeries(series []storage.Series, offset time.Duration)
ev.errorf("smoothed and anchored modifiers do not work with native histograms")
}
// Binary search for the first index with T >= ts.
i := sort.Search(len(floats), func(i int) bool { return floats[i].T >= ts })
// Binary search for the first index with T >= dataTS.
i := sort.Search(len(floats), func(i int) bool { return floats[i].T >= dataTS })
switch {
case i < len(floats) && floats[i].T == ts:
case i < len(floats) && floats[i].T == dataTS:
// Exact match.
ss.Floats = append(ss.Floats, floats[i])
ss.Floats = append(ss.Floats, FPoint{F: floats[i].F, T: evalTS})
case i > 0 && i < len(floats):
// Interpolate between prev and next.
// TODO: detect if the sample is a counter, based on __type__ or metadata.
prev, next := floats[i-1], floats[i]
val := interpolate(prev, next, ts, false)
ss.Floats = append(ss.Floats, FPoint{F: val, T: ts})
val := interpolate(prev, next, dataTS, false)
ss.Floats = append(ss.Floats, FPoint{F: val, T: evalTS})
case i > 0:
// No next point yet; carry forward previous value.
prev := floats[i-1]
ss.Floats = append(ss.Floats, FPoint{F: prev.F, T: ts})
ss.Floats = append(ss.Floats, FPoint{F: prev.F, T: evalTS})
default:
// i == 0 and floats[0].T > ts: there is no previous data yet; skip.
// i == 0 and floats[0].T > dataTS: there is no previous data yet; skip.
}
}

8
promql/promqltest/testdata/extended_vectors.test vendored
View File

@ -434,3 +434,11 @@ eval instant at 15s increase(metric[10s] smoothed)
eval instant at 60s rate(metric[5s] smoothed)
eval instant at 60s increase(metric[5s] smoothed)
# Smoothed vector selector with @ modifier with binary op.
clear
load 10s
metric 0+1x20
eval range from 0s to 60s step 15s metric @ 100 smoothed + 0
{} 10 10 10 10 10