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Resource Advisor - Performance Analytics Forum
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Why does Hierarchy Aggregation disappear after adding a default expression?

If a hierarchy location doesn't have a meter attached, but does have children, you will normally see Energy available as a measurement at that location, and the energy will be the sum of children that are tagged with the value 'Include' for the tag 'AGG_ELECTRICITY'.

If you have supplied a default expression for Electricity:ENERGY (say, to calculate Energy from Demand because that's all your meters supply) then you may be surprised to find that Energy no longer automatically rolls-up through your hierarchy.

It turns out that this 'aggregate tagged children' behaviour is implemented as a 'system supplied' default expression, and that kind of expression is overridden when a user-supplied default expression is attached to a measurement.

So if an expression to derive Energy from Demand is attached to the Electricity:Energy measurement, it supercedes the 'system supplied' default expression that would have done the roll-up. Basically, the AggregateChildren behaviour is replaced with 'derive Energy from Demand'.

The way to reinstate the 'system supplied' default expression is to put it as a location specific formula at all of the parent nodes where it is wanted. 

You need to put


as a location specific formula for Electricity:ENERGY at every node where you want to see its children's energy rolled up.  This formula will take the energy from each tagged child after that energy is calculated from demand using the default expression attached to Electricity:ENERGY.


Re: Why does Hierarchy Aggregation disappear after adding a default expression?

I noticed this the other day Anthony Gray​, thanks for confirming!

For clarity, its mandatory to have this formula to use taggregation?  I always thought the nodes above always aggregated when tagged as agg:electricity, irrespective of the formula.  Maybe just that I never noticed the default measurement.

I suppose my concern is that there may be cases where you want to have a different default measurement,  but on many nodes have to do an aggregation. Any plans on making aggregation using tags more automated (without the need for the formula)?