活动记录外键主键问题

Question

假设我有两个表，它们由自定义列链接：

table1s
  id varchar
  user_id varchar

table2s
  id varchar
  linked_user_id varchar

现在，我尝试在 Ruby 代码中建立关系

class Table1 < ActiveRecord::Base
    self.primary_key = "id"

    has_many :table2s, primary_key: :user_id, inverse_of: :table1
end

class Table2 < ActiveRecord::Base
    self.primary_key = "id"

    belongs_to :table1, foreign_key: :linked_user_id, inverse_of: :table2s
end

现在，当我尝试进行 SQL 查询时，由于某种原因它使用 id 列而不是指定的 user_id

Table2.select('table2s.*')
          .joins(:table1)
          .where('table1s.id = ?', 323235)

生成的 SQL 如下所示：

SELECT table2s.*
FROM table2s
INNER JOIN table1s ON table1s.id = table2s.linked_user_id
WHERE table1s.id = 323235

我原以为是 user_id 而不是 id:

SELECT table2s.*
FROM table2s
INNER JOIN table1s ON table1s.user_id = table2s.linked_user_id
WHERE table1s.id = 323235

有什么想法吗？

Answer 1

如果您的自定义关系中的键与 class (table) 的 primary_key 不同，那么您需要同时添加 foreign_key 和 primary_key 到关系，以便连接正常工作。例如

class Table1 < ActiveRecord::Base
    self.primary_key = "id"

    has_many :table2s, primary_key: :user_id, foreign_key: :linked_user_id, inverse_of: :table1
end

class Table2 < ActiveRecord::Base
    self.primary_key = "id"

    belongs_to :table1, primary_key: :user_id, foreign_key: :linked_user_id, inverse_of: :table2s
end

belongs_to 来自 Docs

:primary_key Specify the method that returns the primary key of associated object used for the association. By default this is id.

has_many 来自 Docs

:foreign_key Specify the foreign key used for the association. By default this is guessed to be the name of the association with an “_id” suffix. So a class that defines a belongs_to :person association will use “person_id” as the default :foreign_key. Similarly, belongs_to :favorite_person, class_name: "Person" will use a foreign key of “favorite_person_id”.

活动记录外键主键问题

Active record foreign key primary key issue

activerecord

ruby-on-rails

ruby-on-rails-5