Ecto order_by

Questions / Help
,
1

In a case where there is default order_by :name :asc, if order_by :type :desc is given, does ecto automatically order them by type first and then name?

%Post{
name : A,
type: free
}

%Post{
name : B,
type: paid
}

%Post{
name : C,
type: free
}

%Post{
name : D,
type: paid
}

In this case, it returns in this order Post B, Post D, Post A, Post C. This is my expected result but I just want to know how this happens.

Thanks! :smiley:

2

Show us how you construct the Ecto query?

3 
def list_posts(criteria \\ %{}) do
    {sort_by, sort_order} = sorters(criteria) || {:name, :asc}

    from(p in Post)
    |> order_by({^sort_order, ^sort_by})
    |>Repo.paginate(
      query,
      [
        before: Map.get(criteria, :before_cursor),
        after: Map.get(criteria, :after_cursor),
        cursor_fields: [{sort_by, sort_order}, :id],
        limit: Map.get(criteria, :limit, 10)
      ])
end

defp sorters(%{sort: %{sort_by: sort_by, sort_order: sort_order}}) do
    {sort_by, sort_order}
  end

I call the function like this Posts.list_posts(%{sort: %{sort_by: :type, sort_order: :desc}, limit: 2})

4

In this case, yes. However sorting by tuple is non-standard behaviour and instead you should provide list of fields instead, so it will be more SQL standard conformant.

5

Do you mind giving more clarity on how it is able to sort by both fields(type and name) when only type is given as sort_by?