I have very simple model with one transaction table and couple of dimension tables. I created a chart wich shows profit for top N customers. The expression is very simple SUM(Profit), Number of customers is some 60,000, Number of rows in the transaction table is 1,500,000.
To Show N top customers I use Dimension Limits. But it takes up to 10 seconds to calculate the chart. If I remove Dimension Limits, Chart is calculated immediatelly.