ruby-on-rails - 在 ID 存在时获取 "Unknown primary key for table"

Question

我一直在调试 Rails 的这个奇怪问题，它给我“表的未知主键...”，即使表的 ID 存在。

我已经将数据库从一个 heroku 应用程序复制到另一个，在原始数据库上没有问题，而新数据库给我一个数据库错误。

这是错误:

ProductsController# (ActionView::Template::Error) "Unknown primary key for table collections in model Collection."

/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/reflection.rb:366:in `primary_key'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/reflection.rb:480:in `association_primary_key'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/association_scope.rb:58:in `block in add_constraints'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/association_scope.rb:39:in `each'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/association_scope.rb:39:in `each_with_index'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/association_scope.rb:39:in `add_constraints'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/association_scope.rb:31:in `scope'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/association.rb:98:in `association_scope'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/association.rb:87:in `scoped'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:573:in `first_or_last'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/collection_association.rb:105:in `last'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/associations/collection_proxy.rb:46:in `last'
/app/app/helpers/likes_helper.rb:62:in `significant_liker'

导致它的行:

product.collections.last.try :user

和表格:

d8apjspa441pad=> \d collections
                                     Table "public.collections"
     Column     |          Type          |                        Modifiers                         
----------------+------------------------+----------------------------------------------------------
 id             | integer                | not null default nextval('collections_id_seq'::regclass)
 name           | character varying(255) | 
 user_id        | integer                | 
 permalink      | character varying(255) | 
 category_id    | integer                | 
 products_count | integer                | 
 is_featured    | boolean                | 
Indexes:
    "index_lists_on_user_id_and_permalink" UNIQUE, btree (user_id, permalink)

知道为什么会发生这种情况吗？

谢谢!

Answer 1

似乎表集合缺少主键。

在 Rails 3.2 之前，像这样在模型中设置主键

class Collection < ActiveRecord::Base
  set_primary_key "my_existing_column"
end

在 Rails 3.2+ 和 Rails 4 中，像这样在模型中设置主键

class Collection < ActiveRecord::Base
  self.primary_key = "my_existing_column"
end

或

我们可以更改表并为id设置主键

创建迁移文件设置主键

class AddPrimaryKeyToCollections < ActiveRecord::Migration
 def change
   execute "ALTER TABLE collections ADD PRIMARY KEY (id);"
 end
end