Hello,
I’ve been trying to implement Ecto.Changeset.optimistic_lock in a Phoenix application but I’m stuck with the generated controller’s update action.

In iex I have success rising an Ecto.StaleEntryError when I try to update a stale record, (as shown in the documentation):

iex> post = Repo.insert!(%Post{title: "foo"})
%Post{id: 1, title: "foo", lock_version: 1}
iex> valid_change = Post.changeset(:update, post, %{title: "bar"})
iex> stale_change = Post.changeset(:update, post, %{title: "baz"})
iex> Repo.update!(valid_change)
%Post{id: 1, title: "bar", lock_version: 2}
iex> Repo.update!(stale_change)
** (Ecto.StaleEntryError) attempted to update a stale entry

here the two changeset are being generated from the same post struct, and Repo.update raise the expected error.

On the other hand, when the update is performed concurrently in two browser windows, -my understanding is that- the controller’s update action performs a new get_post!(id) and then uses that struct to make the update’s changeset, with the form params; therefore the latest update is always overwriting the first occurring, thus making optimistic_lock useless in this context.

I couldn’t find much help on this issue, and it make me think I’m getting all this wrong.. Thank’s for any help.