For example, I have the next schema:

 @primary_key false
  schema "likes" do
    belongs_to :user, User
    belongs_to :post, Post

    timestamps()
  end

And I want to do the next transaction:

  def user_unlikes_post(user_id, post_id) do
    Multi.new
    |> Multi.delete_all(:like, (from Like, where: [user_id: ^user_id, post_id: ^post_id]))
    |> Multi.update_all(:decrement_likes_count, Post.decrement_likes(post_id), [])
    |> Repo.transaction
  end

I’d like to match the result of the delete_all and, if it is not exactly 1, stop the transaction.
I think I could do it with Multi.run but I’d like to know if there is an elegant way to perform this using only “data queries”.

Thanks for your time.