EntityLoader nested relations

[Link184]

I have more entities with chained OneToOne relations, if I do my_model::Entity::load().with(...) only the 1st level of nested relations are loaded. Is there a way to load all of them using the seaorm 2.0?

All the models have simple OneToOne relations using #[sea_orm::model], #[sea_orm(has_one)] #[sea_orm(belongs_to, .......)

Intuitively I expect to have something like:

my_model::Entity::load()
    .with((entity_b, (entity_c, (entity_d, entity_e))))

[For8stt]

Right now EntityLoader::with(...) seems to load only one relation level directly from the root entity.

For deeper has_one / belongs_to chains, I’d probably load it step by step instead of trying to express the whole tree in one .with(...).

Example idea:

let rows = my_model::Entity::load()
    .with(entity_b::Entity)
    .all(db)
    .await?;

Then collect the loaded entity_b ids and load the next level:

let b_ids: Vec<_> = rows
    .iter()
    .filter_map(|row| row.entity_b.as_ref().map(|b| b.id))
    .collect();

let c_rows = entity_b::Entity::load()
    .filter(entity_b::Column::Id.is_in(b_ids))
    .with(entity_c::Entity)
    .all(db)
    .await?;

Not as nice as:

.with((entity_b, (entity_c, (entity_d, entity_e))))

but it keeps the query/result shape explicit and avoids hidden huge joins.

So imo nested .with(...) like that would be a nice feature, but I don’t think it’s currently supported by EntityLoader in SeaORM 2.0.

For now I’d either:

• load each level explicitly
• use a custom join/query if the shape is fixed
• add small helper functions to batch-load the nested one-to-one chain

Would also be useful to have this documented, because the expected syntax is pretty intuitive.

[Link184]

good point, it would be really nice to document it or to fire a warning during compilation.
only my opinion: any orm must hide all the db pain as much as it can, what is the point of using an orm if anyway I am forced to write more db code

[For8stt]

Yeah, I agree. In this case the syntax feels like it should work, so at least having it documented would already help a lot.

A compile-time warning would be even better, but I’m not sure how easy that is to implement cleanly in SeaORM. For now, a short docs section with the current limitation and recommended workarounds would probably avoid a lot of confusion