Question

我在postgresql 9.3上运行Rails 4，我实现了以下多对多关系

第一个模型：

class Cms::ContentEntry < ActiveRecord::Base
  self.table_name = 'cms_content_entries'

  has_many :entries_media, class_name: 'Join::EntryMedia', foreign_key: :cms_content_entry_id
  has_many :media_items, through: :entries_media, class_name: 'Media::Item', source: :media_item
end

加入模型：

class Join::EntryMedia < ActiveRecord::Base
  self.table_name = 'join_entries_media'

  belongs_to :entry, class_name: 'Cms::ContentEntry'
  belongs_to :media_item, class_name: 'Media::Item'
end

第二种模式：

class Media::Item < ActiveRecord::Base
  self.table_name = 'media_items'

  has_many :entries_media, class_name: 'Join::EntryMedia', foreign_key: :media_item_id
  has_many :entries, through: :entries_media, class_name: 'Cms::ContentEntry', source: :entry
end

但是在脚本控制台中，当我运行时：

 Cms::ContentEntry.last.media_items

我收到错误：

 SELECT "media_items".* FROM "media_items" INNER JOIN "join_entries_media" ON    
 "media_items"."id" = "join_entries_media"."media_item_id" WHERE  
 "join_entries_media"."cms_content_entry_id" = $1  [["cms_content_entry_id", 2]]
  PG::UndefinedFunction: ERROR:  operator does not exist: uuid = integer
  LINE 1: ...R JOIN "join_entries_media" ON "media_items"."id" = "join_en...
                                                         ^
  HINT:  No operator matches the given name and argument type(s). You might need to 
  add explicit type casts.: SELECT "media_items".* FROM "media_items" INNER JOIN
  "join_entries_media" ON "media_items"."id" = "join_entries_media"."media_item_id"
  WHERE "join_entries_media"."cms_content_entry_id" = $1

以下是我的架构的样子：

CREATE TABLE cms_content_entries (
    id integer NOT NULL,
    author_id integer,
    title character varying(255),
    body text,
    metadata hstore,
    published_at timestamp without time zone,
    created_at timestamp without time zone,
    updated_at timestamp without time zone
);

 CREATE TABLE join_entries_media (
    id integer NOT NULL,
    cms_content_entry_id integer,
    media_item_id integer
);

 CREATE TABLE media_items (
     id uuid DEFAULT uuid_generate_v4() NOT NULL,
     element_id bigint,
     element_type character varying(255),
     created_at timestamp without time zone,
     updated_at timestamp without time zone,
     user_id integer
);

Answer 1

哎呀，我想通了。基本上，media_items的主键是uuid，而连接表假设主键是整数。

我刚创建了一个迁移，将数据类型更改为uuid：

def change
  create_table :join_entries_media do |t|
  t.integer :cms_content_entry_id
  t.column :media_item_id, :uuid
end

Rails pgsql错误：没有运算符匹配给定的名称和参数类型与多对多

1 个答案: