Heroku的运行耙分贝：迁移错误(heroku run rake db:migrate error

我希望做我的应用程序，我在Heroku上运行迁移，但我得到这个错误：

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

我在我的github仓库以下迁移文件

20120525005302_create_users.rb（里面是空的，不知道如何删除它）
20120611000411_devise_create_users.rb
20120613140535_create_authentications.rb

Answer 1:

它看起来像以下情况：

20120525005302_create_users.rb将尝试创建一个users在数据库中的表。
20120611000411_devise_create_users.rb也将尝试创建一个users数据库表。
你的数据库目前已经有一个users在其表，所以在第二个迁移，迁移失败。

为了让users表在数据库中正确对应20120611000411_devise_create_users.rb迁移，你可以做两件事情之一：

回滚（或下降）的数据库，然后再次运行迁移。（您可以删除20120525005302_create_users.rb如果它是空的。）
修改您的20120611000411_devise_create_users.rb迁移将降大任现有users做其他事情之前表。
修改您的20120611000411_devise_create_users.rb迁移如下：
- 而不是创建的users表，修改现有的表。
- 添加和修改数据库组件对应

一般来说，如果你的应用程序处于“婴儿状态”，然后重新创建数据库往往是构建应用程序的初始结构的快捷方式。不过，如果你已经在你的重要数据users表，你会希望保留并通过修改进行20120611000411_devise_create_users.rb迁移更改数据库的非破坏性。

参考