Yeah, it’s the first method shown in the guide. It’s really just one workaround or another, because the polymorphic association is what I need more or less. Do you have any alternative suggestions? I tried the many-to-many method and it was a nightmare, and the guides are remarkably incomplete on the subject.

I read a few blog posts but they all recommended against the more complex approaches. I had implemented the many-to-many and it was awful, and I considered table inheritance in postgres but was advised against it.

Actually almost my entire domain has these kinds of relationships. I really shouldn’t be using a relational db but I really wanted to use elixir, and I have limited graph db experience so I don’t want to deal with more learning since I’m on a time crunch to get my mvp shipped.

https://mrdotb.com/posts/ecto-exclusive-belongs-to-aka-arc/

What about exclusive belongs to. You make your inbox_items hold fk for all your other models

# you want to left_join and preload the fields
query =
  from(
    item in InboxItem,
    left_join: post in assoc(item, :post),
    left_join: poll in assoc(item, :poll),
    left_join: comment in assoc(item, :comment),
    preload: [
      post: post,
      poll: poll,
      comment:comment 
    ]
  )

items = Repo.all(query, opts)

# I don't think it will be possible to set the virtual_field in the ecto query
# You can do something like below to set it but I think this part should be done
# in the view
Enum.map(items, fn item ->
  model =
    cond do
      is_binary(item.post_id) ->
        item.post

      is_binary(item.poll_id) ->
        item.comment

      is_binary(item.comment_id) ->
        item.comment
    end
   # add the model to the virtual field manually
  %{item | virtual_field: model}
end)