Matthew Roche points out a nice addition to Power Query:
Because of the performance benefit that query folding provides, experienced query authors are typically very careful to ensure that their queries take advantage of the capabilities of their data sources, and that they fold as many operations as possible. But for less experienced query authors, telling what steps will fold and which will not has not always been simple…
Until now.
Read on for more information. I saw this for the first time in a recent presentation and was pleasantly surprised at how well it works.