Having some trouble with a bulk update

    update :backfill_code do
      change fn changeset, context ->
        Ash.Changeset.before_action(changeset, fn changeset ->
          id = Ash.Changeset.get_attribute(changeset, :id)
          guide_id = Ash.Changeset.get_attribute(changeset, :guide_id)

          existing_codes =
            Foobar.Baz
            |> Ash.Query.filter(guide_id == ^guide_id and id != ^id)
            |> Ash.Query.select([:code])
            |> Ash.read!(actor: context.actor)
            |> Enum.map(& &1.code)

          Ash.Changeset.change_attribute(
            changeset,
            :code,
            Foobar.Utils.CodeGenerator.generate_unique_code(id, existing_codes)
          )
        end)
      end

      require_atomic? false
    end

        Ash.bulk_update(Foobar.Baz, :backfill_code, %{},
          actor: actor,
          resource: Foobar.Baz,
          strategy: [:stream],
          return_errors?: true
        )