Performance of rangesum with large volumes of data

[#1]

I am using the following expression to display a cumulative total of sales.

rangesum (above(sales),0,rowno()))

While this expression is working correctly, selections that result in large number of rows takes several minutes to complete. All other object return in seconds with the same row count.

I believe that this is due to the fact that the cumulative total is being recaculated for each row. Any suggestions on how to improve the performance?

[johnw]

You might be able to do something like this:

"Cumulative Sales" = rangesum(above("Cumulative Sales"),"Sales")

With that approach, each line is only looking at the accumulation in the cell above, then adding the Sales for the row to get a new a new cumulative total. The first line is set to "Sales" because above() at that point returns null, and rangesum() treats null as 0.