we are monitoring the power consumption of beamers. They are often plugged off during weekends – in this case, we can not gather any power consumption data. Our typical data looks like this:

We want to visualize the daily consumption in Grafana calculating the daily differences. This query nearly works:

SELECT difference(last("value_number")) 
  FROM "states_history"
  WHERE 
    "dtwin_id" = '57886' 
    AND "state_identifier" = 'stromverbrauch_beamer_gesamt'
    AND $timeFilter 
  GROUP BY time(1d) 
  fill (previous) 

Note: $timefilter is from grafana and inserts the time range selected in the date picker.

This query works perfectly as long as there is at least 1 value per day. But if there is not a single value for the first day of the time range (which often happens on saturdays and sundays when the beamers are plugged off), fill(previous) can not calculate a value and the whole day is not displayed. In the screenshot below, the green bars are for a beamer and monday is missung due to the problem described. The blue bars are for a different measurement with constant data.

This behaviour of fill(previous) is well-known: https://github.com/influxdata/influxdb/issues/6878

Does anyone have a good solution/workaround for this? Maybe, a completely different query could be used? There is some workaround mentioned in the github issue, but only for flux language, not for InfluxQL.

Thanks & regards

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