heroku 运行 rake db：迁移错误

Question

我想在我在 heroku 上的应用程序上运行迁移，但我收到此错误：

Running `rake db:migrate` attached to terminal... up, run.1
DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/1/4/rails-3-2-0-rc2-has-been-released. (called from <top (required)> at /app/Rakefile:7)
DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/1/4/rails-3-2-0-rc2-has-been-released. (called from <top (required)> at /app/Rakefile:7)
DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/1/4/rails-3-2-0-rc2-has-been-released. (called from <top (required)> at /app/Rakefile:7)
Migrating to CreateUsers (20120525005302)
Migrating to DeviseCreateUsers (20120611000411)
==  DeviseCreateUsers: migrating ==============================================
-- create_table(:users)
rake aborted!
An error has occurred, this and all later migrations canceled:

PGError: ERROR:  relation "users" already exists
: CREATE TABLE "users" ("id" serial primary key, "email" character varying(255) DEFAULT '' NOT NULL, "encrypted_password" character varying(255) DEFAULT '' NOT NULL, "reset_password_token" character varying(255), "reset_password_sent_at" timestamp, "remember_created_at" timestamp, "sign_in_count" integer DEFAULT 0, "current_sign_in_at" timestamp, "last_sign_in_at" timestamp, "current_sign_in_ip" character varying(255), "last_sign_in_ip" character varying(255), "created_at" timestamp NOT NULL, "updated_at" timestamp NOT NULL) 

Tasks: TOP => db:migrate

我的 github 存储库中有以下迁移文件

1. 20120525005302_create_users.rb（是空的，不知道怎么去掉）
2. 20120611000411_devise_create_users.rb
3. 20120613140535_create_authentications.rb

Answer 1

您似乎已经有 device_create_users 正在尝试重新创建的表用户（可能来自 create_users 迁移）

您可以修改您的 create_device_users 迁移以仅添加您需要的字段

或者，如果它是一个没有用户的全新应用程序，您可以放弃并尝试重新运行所有迁移

Answer 2

看起来以下是真的：

• 20120525005302_create_users.rb 将尝试在您的数据库中创建一个 users 表。
• 20120611000411_devise_create_users.rb 还将尝试在数据库中创建 users 表。
• 您的数据库中当前已经有一个users 表，因此在第二次迁移时迁移失败。

要使数据库中的 users 表正确对应于 20120611000411_devise_create_users.rb 迁移，您可以执行以下两种操作之一：

1. 回滚（或删除）数据库，然后再次运行迁移。 （如果20120525005302_create_users.rb为空，您可以删除。）
2. 修改您的 20120611000411_devise_create_users.rb 迁移以删除任何现有的 users 表，然后再执行任何其他操作。
3. 修改你的20120611000411_devise_create_users.rb迁移如下：
   • 不要创建users 表，而是修改现有表。
   • 添加和修改数据库组件以对应

通常，如果您的应用程序处于“婴儿期”，那么重新创建数据库往往是构建应用程序初始结构的快速方法。但是，如果您的 users 表中已经有重要数据，您需要保留这些数据并继续修改 20120611000411_devise_create_users.rb 迁移以非破坏性地更改数据库。

参考文献

• Running Rake Commands on Heroku
• RailsGuides: Migrations