I don't really see this as an issue with the Asset Collections, as that is primarily tasked with visualization. Looking at separation of concerns, determining a count is data and thus the task of AF.
If we need to determine a count of elements that have a certain status, the rollup Analysis was meant for that and supports a count of elements that satiesfies a criterium.
Thanks for such reply, but when using roll ups (and we're using some) how can I have a "combined" query triggering on a value?
To illustrate : I want to know how many equipements are out of order knowing each object has a single attribute linked to an enumerated list such as "Off"/"Initialisation"/"Calibrating"/"Running"/"Under maintenance"/"Stopped"/"Out of order".
PI-VISION collection allows to sort on object type and attribute value equals a value from a list.
As far as we known such behaviour is not available with roll up attribute's filter conditions. If a roll up equation allows such combination, of course we can use roll up feature...
We used to bypass such issues by creating extra attributes in AF and count them, but it's not really the best way to do, not the smartest one.
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Yes, you're right. That was cutting corners on my part. It would be great to have attribute value filter capabilities in the rollup. I think this feedback item would cover that: Filter expression for inputs to a Rollup – User Feedback for OSIsoft Products
But there is a workaround: just add an attribute that outputs 0 if your condition is false, and 1 if your condition is true, and use that attribute in a RollUp using the Sum function