Unnecessary callback for conditional statement in SUMX iterator (no column references)

The SUMX iterator uses a conditional IF statement expression that can be rewritten removing unnecessary callbacks to the formula engine. The conditional statement does not reference columns that are part of the data model.

Remarks

The IF function inside an iterator can produce a callback to the formula engine that affects performance. When the iterator is SUMX, it is possible to arrange the code in different ways thanks to the additivity of the result. When the IF condition does not depend on the iterated table, it should be possible to move the condition outside of the iterator, reducing or removing the callback overhead.

Example

Assign the result of the IF function in a variable before the SUMX function and use the variable in the iterated expression.

Original code

SUMX ( 
    Sales,
    Sales[Quantity] * Sales[Net Price] 
        * IF ( MONTH ( TODAY () ) > 6, 1.1, 1 )
)

Possible optimization

VAR _Parameter =
    IF ( MONTH ( TODAY () ) > 6, 1.1, 1 )
RETURN
    SUMX ( 
        Sales,
        Sales[Quantity] * Sales[Net Price] 
            * _Parameter
    )