These singleton instances might seem a good idea, yet since they are only used whenever ORM is booting, the benefit of avoided allocations is limited to this exceptional context.

On the other hand, after having initialized these constants they will take memory in the JVM for as long as it's running; most of these objects are both very fast to build and actually not that small, so I prefer removing the constants, which incidentally happens to be shorter and that's always a nice thing.