[zozbot234]

It's just a different language and a simple "property" layer over the existing data. No changes to the internals are necessary.

[WorldMaker]

No changes are required by PGQ but some engines may wind up using PGQ as a signal to bring in new types of indexes or disk storage formats to back it.

It may be interesting to see if real world usage of PGQ pushes the database engines to do interesting things.