SelectFields will only fire relationship query once and therefore with wrong arguments

[crissi]

I was looking into this https://github.com/rebing/graphql-laravel/issues/602 and fell over this bug.

With this query:

query ($proId: Int, $proId2: Int) {
  test2 {
    name

    alias1: profile(profileId: $proId2) {
      contentType
    }
    
    alias2:profile(profileId: $proId) {
      contentType
    }

  }
}

{
  "proId": 2,
  "proId2": 4,
  "id": 70
}

The profile relationship is only run once and therefore the different arguments given to the custom query clause is not taken into account, only the last query get the right args.

It seems a bit to hard to fix since it is not easily possible to alias eloquent relationships.

Unfortunately something like this is not possible. This would have made it a simplier fix User::with('relationship', 'relationship AS other')->get();

[Pijuli]

How did it end? We ran into the same issue :( Saw the closed PR, but anything else

[crissi]

I made a solution, but it was quite hacky, so it was not accepted, see here: https://github.com/rebing/graphql-laravel/pull/612

[Pijuli]

Yes, I saw it. I can't help as I'm not into the core of it. We managed to make it work by splitting the query... but it'll probably take some more resources. Anyway. I'll keep an eye on the issue. Thanks anyway.

[mfn]

My personal take (as I've expressed in https://github.com/rebing/graphql-laravel/pull/612#pullrequestreview-387360786 ):

I don't think the approach using SelectFields is technically appropriate here. It relies on upfront figuring out everything needed so that the appropriately, possibly nested, SQL relations and stuff can be solved. This results in incredible amount of complexity.

Although the GraphQL spec stays highly absent in talking about how to fetch the data, using dataloaders is a very common and well understood technique.

Since graphql-laravel is a thin wrapper over graphql-php, everything from e.g. https://webonyx.github.io/graphql-php/data-fetching/#solving-n1-problem should apply. And this is in fact how I've approached this in all my projects and it works very well and also is datasource agnostic, as it simply doesn't matter whether it's Eloquent, ElasticSearch, etc.

I would love to be proven wrong, but I don't think this will be solved in SelectFields and ~workarounds~ different approaches to solve this are possible.

[mfn]

Maybe we should add a "caveat" section to the readme and note some known limitations? 🤔

[mfn]

Added to the readme as known limitation