Alex Powers takes us through one major performance optimization technique in Power BI:
One of the most powerful capabilities of Power Query and the M Language is Query Folding (also referred to as query delegation, and predicate push-down). Query Folding allows the Power Query Mashup Engine to push the transformations expressed in an M (mashup) query to the data source, in the data source’s query language, resulting in more efficient data processing.
For inexperienced database technology users this ability to leverage the graphical user interface of Power Query to dynamically generate a query written in the data source’s query language unlocks enormous opportunities to find insights with any data, at any scale.
Click through to see how you can know if query folding is enabled, as well as some hints around when and to what extent query folding will work.