Here is some more context.
The idea is that a user (i.e., author) can create story drafts. Later those can be published. Publishing deletes the StoryDraft and creates a Story. When published, the users can make edits to the published story. In that case a new StoryDraft will be created by copying a large subset of the fields of the published story. If the user commits to the edits made in the new StoryDraft, the published story gets updated and the StoryDraft gets deleted.
stories schema
schema "stories" do
field :title, :string, default: "Untitled Story"
...
has_one :story_draft, StoryDraft
many_to_many(:authors, User,
join_through: "authors_stories",
join_keys: [story_id: :id, author_id: :id],
on_replace: :delete
)
field :published_at, :utc_datetime
timestamps()
end
story_draft schema
schema "story_drafts" do
field :title, :string, default: "Untitled Story"
...
belongs_to :story, Story
many_to_many(:authors, User,
join_through: "authors_story_drafts",
join_keys: [story_draft_id: :id, author_id: :id],
on_replace: :delete
)
timestamps()
end
I am making changes to my schemas, however, because some improvements are necessary. But this is the status quo.
The code snippet from my original post returned a list of maps. I have now changed this to the database returning a list of structs.
def last_updated_stories_and_drafts_by_author(%User{} = user, amount \\ 8) do
story_query =
from s in Story,
join: u in assoc(s, :authors),
where: u.id == ^user.id,
select: [
:id,
:title,
:updated_at,
:cover_image,
:published_at
]
story_draft_query =
from sd in StoryDraft,
join: u in assoc(sd, :authors),
where: u.id == ^user.id,
select: %Story{
id: sd.id,
title: sd.title,
updated_at: sd.updated_at,
cover_image: sd.cover_image,
published_at: nil
}
authors_query =
from a in User,
select: [:id, :username, :verified]
union_query =
from q in story_query,
union: ^story_draft_query,
order_by: fragment("updated_at DESC"),
limit: ^amount,
preload: [authors: ^authors_query]
Repo.all(union_query)
end
As you can see, I used %Story{} as the return struct in the story_draft_query. That works, but feels a bit hacky. The Story struct is a superset, let’s say, of StoryDraft. But that is not enforced in any way (e.g., a marco).
