Data Hub Offloading - Configure Filter predicate for a Measurement value

I would like to offload “all measurements of type X with a value >= 30” via Data Hub. I’m struggling with value part.

I’ve tried using 'src."myfragmentmane."myseriesname"."value" >= 30' in the predicate-filter step of the offloading job. However, this statement does not pass the validation.

Is this a supported Offloading predicate filter? What’s the proper syntax?

Have a try with ‘c8y_Temperature.T.value’ > 30

Thanks, I’ve tried:

  • src.“fragment”.“series”.“value”>30
  • src.fragment.series.value>30
  • fragment.series.value>30
  • “fragment.series.value”>30

but no luck so far. Error message is a generic one: CDHCBEE0441 - Preview computation failed: CDHCBEE0130 - Failed to execute CTAS Job.

Melanie, I just saw your suggestion is using single- rather than double quotes. Can confirm: 'fragment.series.value'>30 passed the valdation. Thanks!

I’m afraid that while you can make the query pass the validation using single-quotes, it doesn’t do what you want. By using single-quotes, you’re creating a string value that is compared against the value 30 – clearly not what you want!

Filtering on a per-fragment/series value is not properly supported (due to the nature of our internal data model in the operational store). There is a way to do it, but I won’t post the solution here as it is nothing I’d recommend to do. DM me if you really need it.

Filtering on custom attributes is supported and simple – the only thing to remember is that if the attribute you want to filter on is nested (i.e. a JSON Object itself), you need to prepend src. to the expression and then “drill” into the structure using dot notation (e.g., src.myObject.myAttribute > 5)

Best, Tim

Thanks! I’ve also just realized that the predicate was accepted using single-quotes - however, it indeed didn’t filter what I desired. For the moment I was mainly interested if it is a supported use case or a matter of missconfiguration => which is answered now.