ruby-on-rails - Heroku 迁移失败 UndefinedTable 错误

Question

我在开发和测试中使用 sqlite，并部署到在生产中使用 Postgres 的 Heroku。我通过在终端中运行以下命令为“评论”创建了一个新模型:

rails g model Review comment:text star:integer room:references reservation:references guest:references host:references type
rails g model GuestReview --parent=Review --migration=false
rails g model HostReview --parent=Review --migration=false
rails db:migrate

这是上述命令的输出:

$ rails g model Review comment:text star:integer room:references reservation:references guest:references host:references type
Running via Spring preloader in process 6862
  invoke  active_record
  create    db/migrate/20180613031058_create_reviews.rb
  create    app/models/review.rb
  invoke    test_unit
  create      test/models/review_test.rb
  create      test/fixtures/reviews.yml

$ rails g model GuestReview --parent=Review --migration=false
Running via Spring preloader in process 6872
  invoke  active_record
  create    app/models/guest_review.rb
  invoke    test_unit
  create      test/models/guest_review_test.rb
  create      test/fixtures/guest_reviews.yml

$ rails g model HostReview --parent=Review --migration=false
Running via Spring preloader in process 6880
  invoke  active_record
  create    app/models/host_review.rb
  invoke    test_unit
  create      test/models/host_review_test.rb
  create      test/fixtures/host_reviews.yml

$ rails db:migrate
== 20180613031058 CreateReviews: migrating 
====================================
-- create_table(:reviews)
-> 0.0806s
== 20180613031058 CreateReviews: migrated (0.0828s) 
===========================

该网站在本地主机上正常运行，当我在 sqlite 中检查数据时，我能够正确保存评论。当我部署到 Heroku 并运行时

heroku run rake db:migrate 

我收到以下错误:

rails aborted!
StandardError: An error has occurred, this and all later migrations canceled:

PG::UndefinedTable: ERROR:  relation "guests" does not exist
: CREATE TABLE "reviews" ("id" serial primary key, "comment" text, 
"star" integer DEFAULT 1, "room_id" integer, "reservation_id" integer, 
"guest_id" integer, "host_id" integer, "type" character varying, 
"created_at" timestamp NOT NULL, "updated_at" timestamp NOT NULL, 
CONSTRAINT "fk_rails_b98b7304fe"
FOREIGN KEY ("room_id")
  REFERENCES "rooms" ("id")
, CONSTRAINT "fk_rails_628a43e51f"
FOREIGN KEY ("reservation_id")
  REFERENCES "reservations" ("id")
, CONSTRAINT "fk_rails_eaa1ce2871"
FOREIGN KEY ("guest_id")
  REFERENCES "guests" ("id")
, CONSTRAINT "fk_rails_ac5cb4d097"
FOREIGN KEY ("host_id")
  REFERENCES "hosts" ("id")
)

这是评论的迁移文件:

class CreateReviews < ActiveRecord::Migration[5.0]
  def change
    create_table :reviews do |t|
      t.text :comment
      t.integer :star, default: 1
      t.references :room, foreign_key: true
      t.references :reservation, foreign_key: true
      t.references :guest, foreign_key: true
      t.references :host, foreign_key: true
      t.string :type

      t.timestamps
    end
  end
end

这是评论模型:

class Review < ApplicationRecord
end

这是 guest_review 模型:

class GuestReview < Review
  belongs_to :guest, class_name: "User"
end

这是 host_review 模型:

class HostReview < Review
  belongs_to :host, class_name: "User"
end

在 Heroku Postgres 上它似乎正在寻找一个不存在的客人表。有没有办法解决此错误，使其在我的开发环境和 Heroku 中正常运行？

Answer 1

在迁移中，t.references :guest, foreign_key: true 做了两件事:

1. 它创建一个名为 guest_id 的整数(或 bigint，具体取决于您的 Rails 版本)列。
2. 它将数据库内部的外键约束从 guest_id 列添加到 guests 表中的 id 列。

但是您要引用的表是users(即User 模型)，而不是guests。由于名称不匹配，您必须调整 t.references调用以告诉 ActiveRecord 要引用哪个表:

t.references :guest, foreign_key: { to_table: :users }

与无法推断表名的任何其他 t.references 调用类似。

---

一旦解决了眼前的问题，您真的应该在开发环境中安装 PostgreSQL，以便您可以在同一个堆栈上进行开发、测试和部署。除了最简单和最琐碎的事情之外，ActiveRecord 不提供数据库可移植性，因此使用不同的数据库进行开发和部署是灾难的根源。