Performace of using LOOKUP and SUM in the same formula

dspar001

I've heard many times not to use LOOKUP and SUM in the same formula because it negatively impacts performace. However, I'm looking at the "calculation effort" cell and it doesn't appear to be negatively impacting performance much at all. I have the option of using some if statements instead of the SUM formula in my equation, but my question what about using a LOOKUP and SUM causes a performance issue and why isn't it reflected in the "calculation effort"?

lgrady

The exception to that rule is when the item you're looking up is a constant. Per the Planual (2.02-08 "never" use sum and lookup together) that is an exception to the rule.

SOURCE:

https://support.anaplan.com/formulas-80dbd4d9-a674-430c-8dd6-87f64db40d29#kqi45scnzy-202-08-never-use-sum-and-lookup-together

2.02-08 Never use SUM and LOOKUP together

SUM and LOOKUP used in the same expression generally cause large formula calculations and may cause intermediate relationship calculations, especially if Time is a dimension or when the source and target structures are very different. Splitting them into different modules and line items considerably reduces the size of the intermediate calculations.

Exceptions

2.02-08a The LOOKUP is a constant	Where the LOOKUP line item is a constant, the formula will operate as a SELECT, so the performance implications are negated.