Performance: Fetching a relationship needlessly loads the whole resource

[carlbennettnz]

As far as I can tell, the following requests are indistinguishable to the database adapter layer.

GET /schools/1
GET /schools/1/relationships/principal

In both cases, the full school resource is loaded. In the latter, everything except for the principal relationship is thrown out by query.returning(). This can get slow for the Knex adapter in cases where other relationships are expensive to load.

An optimisation should be fairly straightforward. I think just setting the select property on the query for relationship requests should do it.

[ethanresnick]

I think just setting the select property on the query for relationship requests should do it.

That works for me! Sounds like the right idea.