I have an interface in my schema:

interface :authentication_source do
  field(:id, non_null(:id))
  field(:name, non_null(:string))
  field(:slug, non_null(:string))
  field(:user_authentications, list_of(non_null(:user_authentication)))

  resolve_type(fn
    %OidcAuthenticationSource{}, _ -> :oidc_authentication_source
    %MicrosoftAuthenticationSource{}, _ -> :microsoft_authentication_source
  end)
end

as well as 2 nodes types that implement that interface:

node object(:oidc_authentication_source, id_fetcher: &authentication_source_id_fetcher/2) do
  field(:name, non_null(:string))
  field(:slug, non_null(:string))
  field(:metadata_document, :string)
  field(:client_id, :string)
  field(:client_secret, :string)
  field(:user_authentications, list_of(non_null(:user_authentication))) do
    resolve(dataloader(Accounts))
  end

  interface(:authentication_source)
end

node object(:microsoft_authentication_source, id_fetcher: &authentication_source_id_fetcher/2) do
  field(:name, non_null(:string))
  field(:slug, non_null(:string))
  field(:tenant_id, non_null(:string))
  field(:client_id, non_null(:string))
  field(:client_secret, non_null(:string))
  field(:user_authentications, list_of(non_null(:user_authentication))) do
    resolve(dataloader(Accounts))
  end

  interface(:authentication_source)
end

The Accounts source is using Dataloader.Ecto and when I run this GraphQL query:

query authenticationSources {
  authenticationSources {
    __typename
    id
    name
    slug
    ... on OidcAuthenticationSource {
      metadataDocument
      clientId
      clientSecret
    }
    ... on MicrosoftAuthenticationSource {
      tenantId
      clientId
      clientSecret
    }
    userAuthentications {
      externalUserId
      user {
        id
        email
        displayName
      }
    }
  }
}

I observe that 2 identical SQL queries are executed to load the :user_authentications:

• 1 query with all the IDs of the authentication sources of type :oidc_authentication_source
• 1 query with all the IDs of the authentication sources of type :microsoft_authentication_source

The dataloader is very helpful but still it is triggering 1 SQL query per type implementing my interface.

I have re-read the following documentations but I cannot find a way to reduce this to a single query :

• Dataloader — absinthe v1.7.10
• Absinthe.Resolution.Helpers — absinthe v1.7.10
• Dataloader — dataloader v2.0.2
• Dataloader.Ecto — dataloader v2.0.2

Is it possible?