Proposal: Type bound functions

[haikyuu]

With the advent of functions with insert/update/delete, it's very tempting to be able to define functions on types themselves. Schema

type Movie {
  title: str;
  multi actors: Actor;
  multi reviews: Review;
  getWithRating: function() {
    select Movie {
      title,
      actors: {
        name
      },
      rating := math::mean(.reviews.score)
    } 
  }
}

And then:

with m := (select Movie limit 1), select m.withRating()

I know it's possible to do a similar behavior by passing a movie as the first parameter. But it's extremely convenient this way. And it would enable moving more of the business logic to the database with a minimal cognitive overhead.

If a schema has 40 types and each type has 2-3 functions:

• Currently, a developer would have to browse through 80-120 functions to find one to use.
• But with this, he wouldn't have to think about it. Plus it would be possible to get autocomplete in queries and client libraries ...

I don't have any stats, but I don't think people define functions all that much either in Postgres nor other databases. Maybe because ORMs don't expose that in a nice way, or maybe they'd rather implement stuff in the programming language.

I think this would be aligned with EdgeDB because it enables offloading more to the database while preserving programming language ergonomics.