N + 1 round trip problem

Does this library handle nested models (joins) in a single query from the server to the DB? For example

user {
  id
  posts {
    id
  }
}

[chanind]

Another option is to use a lazy-loader for SQLAlchemy that is more intelligent about bulk loading. We wrote a custom loader that will inspect the DB session and bulk-load all relations on similar models whenever a relation is lazy-loaded. The result should be the equivalent to using subqueryload on all relations upfront, but without needing any custom code to do so. The loader we wrote is available here in case it’s helpful to anyone else: https://github.com/operator/sqlalchemy_bulk_lazy_loader

[Cito]

Thank you for that blog post @yfilali, that was really helpful.

Your optimize_resolve method works pretty well for me. By using joinedload instead of subqueryload, I was able to reduce a deeply nested GraphQL query into a single database query. I had to add all paths, however, not only the leaves (simply removed the if not p.isLeaf part when assembling the joins).

Another small problem is that in resolve_related you need to translate the field names from GraphQL (camel case) to SQLAlchemy (snake case) with field = to_snake_case(field), otherwise it doesn’t work with table columns with underscores in them. You can import the to_snake_case method from graphene.utils.str_converters.

I feel something like this should be really integrated into graphene-sqlalchemy. Or at least it should provide some helper functions which make it easy to implement such optimized querying, with various loading strategies as options. After all, one of the main advantages of GraphQL over REST is that it solves the N+1 problem. This advantage would be greater if it existed also on the level of the database, not only on the network level.