This was the only point that struck me as well. I believe the author was referring to self-tuning within a general case (ie. as part of the DB software to be de

This was the only point that struck me as well. I believe the author was referring to self-tuning within a general case (ie. as part of the DB software to be deployed against many new databases) rather than one-off ML-based tuning (ie. as part of a manual optimization effort for an existing database). Of course, the real optimization should be for legibility and maintainability... human time being far more important than machine time. But that wouldn't allow fetish discussions diving in to low level efficiencies, now would it? Any sufficiently complex system acts as a black box when it becomes easier to experiment with than to understand. Hence, black-box optimization has become increasingly important as systems become more complex. - Google Vizier: a service for black-box optimization Golovin et al., KDD'17