Scaling with composite models and aggregations

So far, we have discussed how Import mode offers the best possible speed for Power BI datasets. However, sometimes, high data volumes and their associated refresh limitations may lead you to select DirectQuery mode instead. At this point, you may want to review the Choosing between Import and DirectQuery mode section on choosing a storage mode in Chapter 2, Exploring Power BI Architecture and Configuration, to remind yourself about the differences and rationale for choosing one over the other.

We also discussed how the Analysis Services engine is designed to aggregate data efficiently because BI solutions typically aggregate data most of the time. When we use DirectQuery, we want to push these aggregations down to the source where possible to avoid Power BI having to bring all the data over to compute them. With very large tables containing tens of millions to billions of rows, these aggregations can be costly and time-consuming, even...