The code uses a PostgreSQL database.
Prolog is homoiconic so by many in the Prolog community Prolog is also the database.
Is FrameworksBenchmarks requiring that another database be used? If so how much data is being stored? One can store a lot in Prolog without needing another SQL or NoSQL database. (ref)
If the data can be stored with SWI-Prolog using library(persistency) then I would personally consider that they are saddling Prolog with an artificial constraint and that any results for Prolog should not be considered valid. I do understand that there are times when the data is an external database and so Prolog needs to access it as such but if given the choice of using Prolog as the database and using Prolog with an another database I will choose using Prolog as the database. 