Writing dynamic Ecto queries with Composite

There is already an existing article in Ecto docs about dynamic queries https://hexdocs.pm/ecto/dynamic-queries.html so you might think why another article is needed.

Indeed, the article from docs contains a solid foundation. However, I suggest organizing the final code differently. Let's examine the code:

def filter(params) do
  Post
  |> join(:inner, [p], assoc(p, :authors), as: :authors)
  |> order_by(^filter_order_by(params["order_by"]))
  |> where(^filter_where(params))
end

def filter_order_by("published_at_desc"),
  do: [desc: dynamic([p], p.published_at)]

def filter_order_by("published_at"),
  do: dynamic([p], p.published_at)

def filter_order_by("author_name_desc"),
  do: [desc: dynamic([authors: a], a.name)]

def filter_order_by("author_name"),
  do: …

article authors code dynamic elixir filter foundation indeed join params solid