ruby-on-rails - Rails 4.2 引擎引用列迁移失败 PG::UndefinedTable: ERROR: in postgresql

Question

在 Engine I have built 中，我有 3 个类:书籍、类别和作者。每个类的迁移如下。作者和书籍之间以及类别和书籍之间存在一对多关系。引擎将每个类命名为 book_store。在 Postgresql(而不是 sqlite)上使用相同的迁移时，我收到一个错误，其中一个类不存在 PG::UndefinedTable: ERROR: relation "authors"does not exist

我不确定为什么会出现此错误。命名空间也应该在引用中吗？例如，从这个:

  t.references :author, index: true, foreign_key: true
  t.references :category, index: true, foreign_key: true

为此:

  t.references :book_store_author, index: true, foreign_key: true
  t.references :book_store_category, index: true, foreign_key: true

这似乎行不通，因为 BookStore::Books 中会有一个名为 book_store_author 和 book_store_category 的属性导致 BookStore::Books.book_store_author 不会正确地限定在引擎范围内。

我是否需要更改我的迁移代码以在单独的行中反射(reflect)引擎的命名空间？

原始代码

作者

# This migration comes from book_store (originally 20150814153615)
class CreateBookStoreAuthors < ActiveRecord::Migration
  def change
    create_table :book_store_authors do |t|
      t.string :name
      t.text :description
      t.string :slug

      t.timestamps null: false
    end
    add_index :book_store_authors, :slug, unique: true
  end
end

类别

# This migration comes from book_store (originally 20150814153710)
class CreateBookStoreCategories < ActiveRecord::Migration
  def change
    create_table :book_store_categories do |t|
      t.string :title
      t.text :description
      t.string :slug

      t.timestamps null: false
    end
    add_index :book_store_categories, :slug, unique: true
  end
end

书籍

# This migration comes from book_store (originally 20150814153733)
class CreateBookStoreBooks < ActiveRecord::Migration
  def change
    create_table :book_store_books do |t|
      t.string :title
      t.string :lead
      t.text :excerpt
      t.text :description
      t.decimal :price
      t.integer :cover_type
      t.integer :num_pages
      t.string :isbn
      t.integer :year
      t.string :buy_link
      t.string :size
      t.string :cover_image
      t.string :slug
      t.references :author, index: true, foreign_key: true
      t.references :category, index: true, foreign_key: true

      t.timestamps null: false
    end
    add_index :book_store_books, :slug, unique: true
  end
end

错误:

/home/deploy/apps/saturnalia_books/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.3/lib/active_record/migration.rb:797:in `migrate'
/home/deploy/apps/saturnalia_books/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.3/lib/active_record/tasks/database_tasks.rb:137:in `migrate'
/home/deploy/apps/saturnalia_books/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.3/lib/active_record/railties/databases.rake:44:in `block (2 levels) in <top (required)>'
ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  relation "authors" does not exist
: ALTER TABLE "book_store_books" ADD CONSTRAINT "fk_rails_52f80cb3c5"
FOREIGN KEY ("author_id")
  REFERENCES "authors" ("id")
/home/deploy/apps/saturnalia_books/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.3/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `async_exec'
/home/deploy/apps/saturnalia_books/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.3/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `block in execute'


   ...

  PG::UndefinedTable: ERROR:  relation "authors" does not exist

编辑

here is the full stack trace

Answer 1

我通过如下更改模型和迁移文件解决了这个问题。

我有 blog 模型，它通过 tagging 模型有很多 tags。

所以我更新了 tagging 模型看起来像这样

module Blog
    class Tagging < ActiveRecord::Base
      belongs_to :tag, :class_name => "Blog::Tag"
      belongs_to :post, :class_name => "Blog::Post"
   end
 end

然后我像这样修改了 post 模型。

module Blog
  class Post < ActiveRecord::Base
    has_many :taggings, :class_name => "Blog::Tagging"
    has_many :tags, through: :taggings
  end
 end

迁移文件修改如下

class CreateBlogTaggings < ActiveRecord::Migration
 def change
   create_table :blog_taggings do |t|
    t.integer :tag_id, index: true, foreign_key: true
    t.integer :post_id, index: true, foreign_key: true
 end
end

因此，在您的情况下，将 t.references :author 更改为 t.integer :author _id 并将 t.references :category 更改为 t.integer :category_id.

这应该可以解决您的迁移问题。