I don't quite follow. For a system reliant entirely on Postgres, you can just fetch the records, and join them in real time, no? It would be much slower than elasticsearch, but still _good enough_ for a lot of use cases.
What I really want is an integration between Instantsearch.js, and Postgres.
Typesense has written a custom adapter for Instantsearch & Typesense. I would love to just hook Instantsearch up to directly to my rails all. You could use pg_search to get 90% of the value, with next to no complexity on the backend.