Difference between InfluxQL and Flux concerning derivative #4942

Hello there !
Working on translating InfluxQL to Flux on Grafana, I’ve seen that the Flux derivative function does not seems to work like the InfluxQL non_negative_derivative concerning timestamp. In fact, when doing the derivative between values at time A (older) and time B, InfluxQL returns the value with timestamp A whereas Flux returns it with timestamp B
(Top graph is the InfluxQL query, bottom one is the Flux query)

The values I’m working on are returned by Telegraf, and in the early seconds of a minute the last value is way higher with Flux than with InfluxQL, and I sometimes get really high peak that decreases with time

Is there a way to solve this ?

For info:
InfluxQL query:

SELECT non_negative_derivative(mean("FIELD"), 1s) FROM "MEASUREMENT" WHERE ("VARIABLE" =~ /^$VARIABLE$/) AND $timeFilter GROUP BY time($__interval) fill(null)

Flux query:

from(bucket: "BUCKET")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r["_measurement"] == "MEASUREMENT")
  |> filter(fn: (r) => r["_field"] == "FIELD")
  |> filter(fn: (r) => r["VARIABLE"] =~ /^${VARIABLE:regex}$/)
  |> set(key: "alias", value: "TPS")
  |> group(columns: ["alias"])
  |> aggregateWindow(every: v.windowPeriod, fn: mean)
  |> derivative(unit: 1s, nonNegative: true)

Hello @MiniPierre,
First, thank you for creating an issue. You rock!
I’ve also created this issue:

You can use:

|> timeShift(duration:  - <duration between points>)   

To “fix” the timestamp, but I don’t think this will fix the results you’re seeing at the tale end.

Thank you for the issue !
Sorry for the duplicated message with GitHub, I saw the community was quite reactive so I posted it here afterwards