Comment by banana_feather

I like the author's datalog work generally, but I really wish his introductory material did not teach using binary join, which I found to get very messy internally as soon as you get away from the ideal case. I found the generic join style methods to be much, much simpler to generalize in one's head (see https://en.wikipedia.org/wiki/Worst-case_optimal_join_algori...).