This is really good advice and is what I ended up doing.
So to help anyone who’s stuck with a similar problem, here is my less-heavyweight query(I only Ecto.preload :mediaitemartifacts at first).
from(m in MediaItem,
join: con in ContentMediaItems,
on: m.id == con.media_item_id,
where: is_nil(m.published_at) == false,
join: chan in assoc(con, :channel),
where: chan.id == con.channel_id,
join: org in Org,
on: m.org_id == org.id,
where: org.slug == ^org_slug,
order_by: [{:desc, :published_at}],
preload: [:mediaitemartifacts],
select: %{id: m.id, inserted_at: m.inserted_at, media_item: m, channel: chan}
)
and later on, in the controller, I Repo.preload() the contents:
list =
Enum.map(list, fn %{media_item: media_item, channel: channel} ->
%{media_item: media_item, channel: Repo.preload(channel, :contents)}
end)
