Ecto联接表验证

Question

我的联接表名为：seasons_teams

  schema "seasons_teams" do
    field(:score, :integer)
    belongs_to(:season, Season, foreign_key: :season_id, type: :binary_id)
    belongs_to(:team, Team, foreign_key: :team_id, type: :binary_id)

    timestamps()
  end

这很好，但我想验证season和team的重复项不存在。

例如：

  %MyApp.SeasonsTeams{
    __meta__: #Ecto.Schema.Metadata<:loaded, "seasons_teams">,
    id: "89ec0dbd-cc61-4ba9-8dcf-b86b858d2882",
    inserted_at: ~N[2019-11-10 00:58:27],
    score: nil,
    season: #Ecto.Association.NotLoaded<association :season is not loaded>,
    season_id: "79c4bd04-d362-495c-ab13-649b299c23e2",
    team: #Ecto.Association.NotLoaded<association :team is not loaded>,
    team_id: "b6c408ef-d48e-4de9-8a46-8ae7bb12b699",
    updated_at: ~N[2019-11-10 00:58:27]
  },
  %MyApp.SeasonsTeams{
    __meta__: #Ecto.Schema.Metadata<:loaded, "seasons_teams">,
    id: "89a7fc61-6ce4-4a6d-a9dc-8e3494378e33",
    inserted_at: ~N[2019-11-10 00:58:37],
    score: nil,
    season: #Ecto.Association.NotLoaded<association :season is not loaded>,
    season_id: "79c4bd04-d362-495c-ab13-649b299c23e2",
    team: #Ecto.Association.NotLoaded<association :team is not loaded>,
    team_id: "b6c408ef-d48e-4de9-8a46-8ae7bb12b699",
    updated_at: ~N[2019-11-10 00:58:37]
  }

您会看到这两个记录具有相同的season_id和相同的team_id，我不希望这样做。我很好奇Phoenix / Elixir / Ecto是否提供了处理这种情况的好方法？谢谢！

Answer 1

在跨越两个字段的表上创建唯一索引，并使用unique_constraint验证唯一约束：

unique_constraint