Maybe it means (trying to read charitably) that those are the methods, and if a suboptimal one of them (for a given query, schema, etc.) is chosen, then ... Or

Maybe it means (trying to read charitably) that those are the methods, and if a suboptimal one of them (for a given query, schema, etc.) is chosen, then ... Or it's just a continuation of the first point: any non-application join is suboptimal. (Erm..) Edit: in fact, re-reading TFA, I think it is the latter or something like it - because the shift to application logic is mentioned as a 'countermeasure' for the 'suboptimal join methods'. I think it means deal with sometimes getting a bad plan by taking control and doing it yourself in the application. (I don't agree, just trying to understand.)