Reza Rad does a bit of configuration:
Aggregation can speed up the performance of DirectQuery sourced tables significantly. To use it, firstly, you need to create an aggregation table. Secondly, you must set up proper storage modes for tables in the model. Finally, you have to configure the aggregation functions, which I will explain in this post. You can learn about aggregation in other posts of this series and continue the example here. If you like to learn more about Power BI, read the Power BI book from Rookie to Rock Star.
Read on to learn more.