Seriously, why is this one of the top stories on HN? These types of tests are so easy to tweak in favor of a perferred database that they are completely unreliable. Even neutral comparisons by third parties are rife with errors like not adding proper indices to all the DBs or using query formulations that avoid the indices on some DBs or other configuration issues (DBs are unfortunately tricky.)
I think the only way to do this objectively is to have a test and then give each DB vendor an opportunity to tweak the DB and queries to optimize performance. Seeing how DB vendors optimized performance would actually be very informative to potential users. Everything else is just a comedy of errors (or worse) as normally people usually only have good expertise in one of the DBs in question, if that.