Question

我正在关注Lynda ruby on rails教程。我已经运行了代码＆＃34; rake db：migrate＆＃34;经过几次不成功的尝试。然后我被告知要运行＆＃34; rake db：migrate VERSION = 0＆＃34;。这再一次给了我错误，这次我无法修复它。我昨晚和今天早上都试过无济于事。

请记住，在回答我是新手编码时，请以新手可以理解的方式解释。

lexi87$ rake db:migrate VERSION=0
==  AlterUsers: reverting =====================================================
-- remove_index("admin_users", "username")
rake aborted!
An error has occurred, all later migrations canceled:

Index name 'index_admin_users_on_username' on table 'admin_users' does not exist
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/connection_adapters/abstract/schema_statements.rb:587:in `index_name_for_remove'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/connection_adapters/abstract/schema_statements.rb:366:in `remove_index'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:466:in `block in method_missing'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:438:in `block in say_with_time'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:438:in `say_with_time'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:458:in `method_missing'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:334:in `method_missing'
/Users/lexi87/Sites/simple_cms/db/migrate/20130108015542_alter_users.rb:14:in `down'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:376:in `down'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:410:in `block (2 levels) in migrate'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:410:in `block in migrate'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/connection_adapters/abstract/connection_pool.rb:129:in `with_connection'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:389:in `migrate'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:528:in `migrate'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:720:in `block (2 levels) in migrate'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:777:in `call'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:777:in `ddl_transaction'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:719:in `block in migrate'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:700:in `each'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:700:in `migrate'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:574:in `down'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/migration.rb:555:in `migrate'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/gems/activerecord-3.2.9/lib/active_record/railties/databases.rake:179:in `block (2 levels) in <top (required)>'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/bin/ruby_noexec_wrapper:14:in `eval'
/Users/lexi87/.rvm/gems/ruby-1.9.2-p320/bin/ruby_noexec_wrapper:14:in `<main>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

这是rb文件。

class AlterUsers < ActiveRecord::Migration

  def self.up
    rename_table("users", "admin_users")
    add_column("admin_users", "username", :string, :limit => 25)
    change_column("admin_users", "email", :string, :limit => 100)
    rename_column("admin_users", "password", "hashed_password")
    add_column("admin_users", "salt", :string, :limit => 40)
    puts "*** About to add an index ***"
    add_index("admin_users", "username")
  end

  def self.down
       remove_index("admin_users", "username")
       remove_column("admin_users", "salt")
       remove_column("admin_users", "hashed_password", "password")
       remove_column("admin_users", "email", :string, :default => "", :null => false)
       remove_column("admin_users", "username")
       rename_table("admin_users", "users")
  end

end

Answer 1

rake db：migrate VERSION = 0 回滚所有迁移

错误明确表示

Index name 'index_admin_users_on_username' on table 'admin_users' does not exist

我怀疑你实际上是在尝试回滚从未应用的迁移，因此索引不存在。或者，您已在应用迁移后对其进行更改。我的建议是删除数据库，再次创建并应用所有迁移。

rake db:drop
rake db:create
rake db:migrate

Answer 2

您正在删除不存在的索引。始终使用以下顺序：

1）rake db：create

2）rake db：migrate

此外，在您收到的错误的上下文中，请记住rake db:migrate VERSION=0将删除所有迁移，如果这是您正在尝试执行的操作，并且因为之前没有索引，那么它将通过错误。

我还怀疑包含mysql设置的database.yml文件的凭据错误，尤其是username和password的设置。检查并更正它，然后进行迁移。

Answer 3

猜 1.你不能跳回到其他版本（它总是在终端上显示错误）。你也不能耙db：rollback＆＃39; 你不能耙db：向下迁移＆＃39;同样。你正在使用MySQL。

深吸一口气，尝试这样做。

一个。打开终端应用程序，然后输入。

rake db:drop

之后，尝试查看您的数据库。必须没有＆＃34;您的数据库＆＃34;。

B中。重新创建数据库（直接使用MySQL命令或跟进Rake命令）对于MySQL

CREATE DATABASE database_name;

for Rake

rake db:create

尤金先生回答说。

℃。进行迁移，转到终端并输入。

rake db:migrate

之后，您应该登录到您的数据库以检查其上的任何活动。

rake db：migrate VERSION = 0表不存在

3 个答案: