What does Tableau 9.1 mean for your LOD expressions?

Tableau 9.1 is out. You may not see much mention of this in the list of improvements/features in 9.1 but you will notice that some of your LOD calculations will run MUCH faster. As I mentioned in my LOD expression introductory blog post, Tableau 9.0 runs each LOD expression as a separate subquery. Hence as you add more LOD expressions to your sheets, you probably noticed some performance degredation.  In 9.1, Tableau will collapse the subqueries for LOD expressions that operate at the same dimensionality and filter context. Result is up to 24x performance improvement in our TPC-DS tests!