Backlinks and type filter operator in ORM

[vpetrovykh]

We need a way to access backlinks in ORM. As we know the backlinks need a name and a source type to be properly defined. However in pure EdgeQL we allow bare backlinks (which then get inferred as Object type) and we treat the backlink .< operator separate from type filtering [is Foo].

Should we have __backlink__ available in Python? Do we pass the type as an argument?

q = default.User.filter(lambda u: u.__backlink__.members(default.Group).name = 'admin')

Will we have some kind of separate type filter operator exposed in Python? Can I translate something like:

select User {
  name,
  # assume the schema has type Bot extending User
  special := .friends[is Bot],
}

It could be std.is_type(...) maybe? Would that mean that backlinks then become something like: std.is_type(u.__backlink__.friends, default.Bot) or std.is_type(u.__backlink__.members, default.Group)?

Ideally, I'd prefer not to pollute the plain fields of reflected types with all the backlinks directly, hence the __backlink__ intermediary.

[scotttrinh]

FWIW, in the TypeScript query builder we do pollute the main fields with all possible backlinks and it's not a huge deal. Helps with discoverability, too. u[".<friends[is Bot]"] is what that looks like. People find it just as offputting as backlinks in general, but doesn't seem to be an actual hinderance once they get used to it.

[vpetrovykh]

We use the stuff we reflect as pydantic types to also specify fields in constructors or in validators. Polluting these with all the backlinks is not a good idea IMO.