count function performance issue

[mathil]

Is there a way to improve performance on the count function in report studio. I want to count the number of orders with a revenue larger than 0 per sales staff. The order dimension is of course very large as is the client dimension. I have tried different approaches all having a very negative effect on performance. What would the best practice solution to this problem.

Creating count as:

count([order] within set( filter([order]; [revenue] > 0 ) ))

Adding a count to the table doesnt seem to help either.