在Elixir中使用Ecto，这无法评估现有索引的唯一限制

Question

>我有一个现有的数据库，并且该表中有一个唯一的索引

ALTER TABLE ONLY users ADD CONSTRAINT unique_document_id UNIQUE (document_id);

我在 Ecto 中没有任何迁移，我想使用变更集插入一条新记录。这是模型中的代码和要插入的代码

defmodule User do
  use Ecto.Schema
  schema "users" do
    field :name
    field :email
    field :document_id
  end
  def signup(name, id_number, email) do
    changeset = User.changeset(%User{}, %{name: name,
                                            email: email,
                                            document_id: id_number})
    if changeset.valid? do
      IO.inspect "the chagenset is valid"
      user = case Repo.insert(changeset) do
        {:ok, model}        -> {:ok, model }
        {:error, changeset} -> {:error, changeset.errors}
      end
   end

def changeset(driver, params \ :empty) do
    driver
    |> cast(params, [:document_id, :email, :name])
    |> validate_required([:document_id, :email, :name])
    |> unique_constraint(:document_id)
    |> unique_constraint(:email)
  end

  end
end

但是当我尝试插入重复的用户时，我收到此错误并且 changeset.valid？ 是真的

11:04:17.896 [error] #PID<0.434.0> running App terminated
Server: localhost:4000 (http)
Request: POST /api/signup
** (exit) an exception was raised:
    ** (Ecto.ConstraintError) constraint error when attempting to insert struct:
    * unique: unique_document_id
If you would like to convert this constraint into an error, please
call unique_constraint/3 in your changeset and define the proper
constraint name. The changeset defined the following constraints:
    * unique: users_document_id_index
        (ecto) lib/ecto/repo/schema.ex:493: anonymous fn/4 in Ecto.Repo.Schema.constraints_to_errors/3
        (elixir) lib/enum.ex:1229: Enum."-map/2-lists^map/1-0-"/2
        (ecto) lib/ecto/repo/schema.ex:479: Ecto.Repo.Schema.constraints_to_errors/3
        (ecto) lib/ecto/repo/schema.ex:213: anonymous fn/13 in Ecto.Repo.Schema.do_insert/4
        (ecto) lib/ecto/repo/schema.ex:684: anonymous fn/3 in Ecto.Repo.Schema.wrap_in_transaction/6
        (ecto) lib/ecto/adapters/sql.ex:620: anonymous fn/3 in Ecto.Adapters.SQL.do_transaction/3
        (db_connection) lib/db_connection.ex:1275: DBConnection.transaction_run/4
        (db_connection) lib/db_connection.ex:1199: DBConnection.run_begin/3

Answer 1

>您需要在调用unique_constraint时指定约束名称，因为它不是默认的 Ecto 约定(如错误消息所示，这将是users_document_id_index(：

|> unique_constraint(:document_id, name: :unique_document_id)

如果您的电子邮件也有唯一的约束名称，但该名称不是users_name_index，则还需要对unique_constraint(:name)执行相同的操作。