Need help optimizing a multi level DAX summarize calculation - sql

Question

I'm looking for advice on how to optimize a multi-level DAX summarize query. This one is very slow because, I think, it is running O(n^3) because of the nesting. Unfortunately, i need to have several levels because the hierarchy levels Order > Order Line > Order Detail need to be calculated differently.
Units need to sum up to the Detail level
That needs to be averaged up to the Line level
That needs to be summed up to the Order level
SUMX(
SUMMARIZE(
'FACT Opportunity'
,Opportunity[LineId]
,"Units"
,AVERAGEX(
SUMMARIZE(
'FACT Opportunity'
,Opportunity[DetailId]
,"SumDetail"
,SUM('FACT Opportunity'[Units])
)
,[SumDetail]
)
)
,[Units]
)
Any help or advice you could provide would be very much appreciated.

Answer 1

It's very hard to provide an optimisation advise without seeing the data and data model (it'd be great if they were included in the question).
The key issue here is that the presence of the duplicates makes fact "Units" non-additive, meaning that you can't simply roll it up the hierarchy. As a result, you are forced to do a very expensive triple-looping.
An obvious solution then is to make "Units" fully additive. You can compute de-duplicated (adjusted for duplicates) Units and store them in fact Opportunity, as a calculated column:
Adjusted Units =
DIVIDE (
'FACT Opportunity'[Units],
CALCULATE ( COUNT ( 'FACT Opportunity'[DetailId] ) )
)
Here, you divide Units by the number of unique DetailIDs (usually, it will be 1, but in case of duplicate DetailIDs it will be 2, etc).
This calculated column will increase your data loading time a bit, but save a lot of query time. To further optimize, consider pre-calculating it in a data warehouse.
The adjusted Units are fully additive, so you dax is now simple:
Total Units = SUM('FACT Opportunity'[Adjusted Units])
It should work correctly on any level of the Order > Line > Detail hierarchy (unless there are additional problems not described in the question), and it should be fast.