unique_constraint无法识别2个字段

您没有完成更改集功能.

presence =
  %Presence{ user_id: result.id, event_id: val, state: Presence.get_assigned }
  |> Repo.insert!

应该:

presence =
  Presence.changeset(%Presence{}, %{user_id: result.id, event_id: val, state: Presence.get_assigned})
  |> Repo.insert!