Ecto中`many_to_many`关联的外键名称

这里是一个关于many_to_many关联的问题。我得到的错误是Ecto中`many_to_many`关联的外键名称

INSERT INTO "qbinders" ("title","typecode","inserted_at","updated_at","id") VALUES ($1,$2,$3,$4,$5) ["Math", "Jim1000", {{2017, 4, 1}, {15, 4, 47, 827009}}, {{2017, 4, 1}, {15, 4, 47, 843348}}, <<68, 1 
49, 156, 219, 153, 214, 65, 63, 179, 141, 252, 147, 221, 247, 41, 143>>] 
[debug] QUERY OK db=0.9ms 
commit [] 
** (Postgrex.Error) ERROR 42703 (undefined_column): column q2.qbinders_id does not exist

运行

qbinder_map = %{ title: "Math", typecode: "Jim1000"} 
changeset = Qbinders.changeset(%Qbinders{}, qbinder_map) 
qbinder = Repo.insert!(changeset) |> Repo.preload(:qbooks) 

qbook_list = 
    %Qbooks{ title: "Algebra1"} 
qbook = Repo.insert!(qbook_list) |> Repo.preload(:qbinders) 

changeset = Ecto.Changeset.change(qbinder) 
      |> Ecto.Changeset.put_assoc(:qbooks, [qbook_list]) 
Repo.update!(changeset)

Postgres里，连接表看起来像

CREATE TABLE qbook2qbinder 
(
    qbook_id uuid, 
    qbinder_id uuid, 
    qbook_order integer, 
    inserted_at timestamp without time zone NOT NULL, 
    updated_at timestamp without time zone NOT NULL, 
    CONSTRAINT qbook2qbinder_qbinder_id_fkey FOREIGN KEY (qbinder_id) 
     REFERENCES qbinders (id) MATCH SIMPLE 
     ON UPDATE NO ACTION ON DELETE NO ACTION, 
    CONSTRAINT qbook2qbinder_qbook_id_fkey FOREIGN KEY (qbook_id) 
     REFERENCES qbooks (id) MATCH SIMPLE 
     ON UPDATE NO ACTION ON DELETE NO ACTION 
)

和模型是

defmodule Project.Qbinders do 
    use Project.Web, :model 

    @primary_key {:id, :binary_id, autogenerate: true} 

    schema "qbinders" do 

     field :title, :string 
     field :reward, :string 

     many_to_many :qbooks, Project.Qbooks, join_through: "qbook2qbinder" 
    timestamps 
    end

为什么Ecto会寻找qbinders_id而不是qbinder_id？我如何将它设置为qbinder_id？

来源

2017-04-01 Jason O.

我怀疑这是因为您的型号名称为'Qbinders'，正因为如此，列名是从名称派生。您应该可以使用'join_keys'关键字参数自行配置关联 - 请检查此[doc]（https://hexdocs.pm/ecto/Ecto.Schema.html#many_to_many/3-选项） –

Spot。谢谢。如果你添加答案，我会接受它。 –

很高兴帮助！干杯! –

这可以通过的参数Ecto.Schema.many_to_many/3轻松定制。

列名可使用选项join_keys进行配置，并且应该像使用：

many_to_many :qbooks, Project.Qbooks, join_through: "qbook2qbinder", 
             join_keys: [{qbook_id: :id, qbinder_id: :id}]

来源

2017-04-01 20:28:40

Ecto中`many_to_many`关联的外键名称

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