I don't think I've ever been so happy to get basic join support working. Expressivity usually comes at the expense of performance, and we are aiming for a TON of expressivity in #Draupnir.

It's been a heck of a time getting the "good" cases to optimize down to what a standard database would do (e.g., simple Hash Joins), but the end is in sight... The group theory bits are (mostly) implemented, and now we just need to deal with simple operational issues like the scheduler freaking out when it tries to poke an unordered CSV file for a cursor that supports indexed seeks.

The effort is worth it though... with this latest change, we should be able to support the ring-style factorization optimizations you get in #DBToaster, while simultaneously supporting non-ring aggregates like Min and Max like #Souffle, as well as #Rel's map relations.

The project name seems more apropos than we realized when we first named it... The key insight has been the realization that we need to give up the ring (and settle for the monoid/group).