PostGraphile is the new incarnation of PostGraphQL (project history), which introspects your Postgres database schema and creates a fully functional GraphQL API for it.
I've been poking around with these tools as I get acquainted with the provider side of GraphQL. I don't think we'll end up using PostGraphile if/when we ship our public Changelog API (news + podcasts), because I'm a control freak. But it's been great for getting started quickly and seeing what's possible. Highly recommended 👌