This article describes the behavior of the COMBINEVALUES function in DAX, and how it can optimize the performance of DirectQuery with multi-column relationships.  Read more

This article describes how DAX Studio can analyze the SQL queries sent to a relational database by Power BI or Analysis Services Tabular in DirectQuery mode.  Read more

This article describes a few query limits existing in DirectQuery for both Power BI and Analysis Services Tabular 2016, explaining when you can modify them.  Read more