What is the cost of iterators in DAX?

< 1 min read

Iterators in DAX, like SUMX or FILTER, compute row by row, which increases CPU and memory usage.
In one project, SUMX over a 2-million-row fact table caused slow visual rendering.
Each row triggers evaluation of the expression, multiplying calculation cost.
Nested iterators amplify the performance impact exponentially.
High-cardinality columns worsen the processing time.
Replacing iterators with aggregated measures reduced query load.
Using variables inside iterators can prevent repeated calculations.
So iterators are powerful but expensive and should be used judiciously.

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