Forum Discussion
DAX Measure Optimization - Please help
Hi Sir, Thank you for your reply! There is indeed a relationship between DimKPI and FactProductivity via key "KPIKey". However, when I use the version that you suggested I received the following error "A single value for column 'KPIKey' in table 'DimKPI' cannot be determined. This can happen when a measure or function formula refers to a column that contains many values without specifying an aggregation such as min, max, count, or sum to get a single result."
This is fine though, I will use the TRETAS measure that you confirmed is definitely the best alternative to the original measure. Thanks a lot again!
Hi NRF95 ,
First, What your original measure is really doing?
Your original measure:
- Creates a virtual table grouped by
- FiscalMonth × CustomerKey
- For each group, evaluates
- DISTINCTCOUNTNOBLANK ( FSOLastEmployeeKey )
- Applies KPIKey = 271
- Then SUMX over the virtual table
So the expensive parts are:
- CALCULATETABLE + SUMMARIZECOLUMNS
- Nested CALCULATE
- Row-by-row SUMX
Evaluation of your solutions
Solution A - Why it’s NOT optimal?
- Forces context transition inside SUMX
- DISTINCTCOUNT is re-evaluated row by row
- Filter is applied outside, not pushed into the grouping
- Works logically, but worst engine plan of the 3
Solution B - Why this is better?
- KPI filter pushed inside SUMMARIZECOLUMNS
- No nested CALCULATE per row
- Cleaner filter propagation
- Better storage engine utilization
- Solution B is clearly better than A
Best Optimized Version (Better than both):
You can remove the virtual column entirely and let the engine aggregate directly:
---DAX---
CY Periodical - OMNI - # Actual Covering Agents :=
CALCULATE (
SUMX (
SUMMARIZECOLUMNS (
FactProductivity[FiscalMonth],
FactProductivity[CustomerKey]
),
DISTINCTCOUNTNOBLANK ( FactProductivity[FSOLastEmployeeKey] )
),
DimKPI[KPIKey] = 271
)
---DAX---
Why this is the best?
- No nested CALCULATE
- No calculated column inside SUMMARIZE
- KPI filter applied once
- Storage Engine can optimize DISTINCTCOUNT
- Same logic, fewer formula engine calls
Solution A → logically correct, performance regression
Solution B → better, safe improvement
Final version above → best optimized, same logic, best engine plan
=================================================================
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