rails“rake db:migrate”迁移部分完成，需要从头开始重做

Question

我是 ruby​​-on-rails 的新手，并且遇到了困难。

我试着跑 "rake db:migrate" 但由于有错字而被中止。我输入了“用户”而不是“用户”。 因此，我修复了 db/migrate 目录中的 rb 文件并尝试再次运行它，但发现迁移已经部分进行，我无法再次重做。这似乎是像我这样的初学者的常见错误，讲师为此提出了两种解决方案：首先 DROP 中的 SQL 表或第二个 COMMENT OUT 已经运行的部分并运行剩余部分。

但在找到故障排除建议之前，我认为我可以使用不同的文件名 (SIGH)，我将“用户”更改为“管理员用户”，将“管理员用户”更改为“管理员用户 2” '。 我没有工作，我放下桌子做了

$ rails 生成迁移 AlterUsers 和 $ rake db:迁移

但它再次中止，因为它找不到这个文件：users.frm。 （我不知道 .frm 文件在哪里……）

非常感谢。

---------------错误信息------ ----------------------

$ rake db:migrate
==  AlterUsers: migrating =====================================================
-- rename_table("users", "admin_users")
rake aborted!
An error has occurred, all later migrations canceled:

Mysql2::Error: Can't find file: './simple_cms_development/users.frm' (errno: 2 - No such file or directory): RENAME TABLE `users` TO `admin_users`/Users/gymmilo/Sites/simple_cms/db/migrate/20130927112013_alter_users.rb:3:in `change'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

---------------迁移文件------ ----------------------

class AlterUsers < ActiveRecord::Migration
  def change
    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
end

------------------(我已经把桌子掉了一次，结果是这样的！谢谢帮助. --------

mysql> SHOW TABLES;
+----------------------------------+
| Tables_in_simple_cms_development |
+----------------------------------+
| admin_users1                     |
| schema_migrations                |
+----------------------------------+
2 rows in set (0.00 sec)

mysql> DROP TABLE admin_users1;
Query OK, 0 rows affected (0.01 sec)

mysql> exit
Bye
$ rake db:migrate
==  AlterUsers: migrating =====================================================
-- rename_table("users", "admin_users")
rake aborted!
An error has occurred, all later migrations canceled:

Mysql2::Error: Can't find file: './simple_cms_development/users.frm' (errno: 2 - No such file or directory): RENAME TABLE `users` TO `admin_users`/Users/gymmilo/Sites/simple_cms/db/migrate/20130927112013_alter_users.rb:3:in `change'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)
$ mysql -u simple_cms -p simple_cms_development
Enter password: 
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 43
Server version: 5.6.13 Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> SHOW TABLES;
+----------------------------------+
| Tables_in_simple_cms_development |
+----------------------------------+
| schema_migrations                |
+----------------------------------+
1 row in set (0.00 sec)

mysql> exit
Bye
$ pwd
/Users/gymmilo/Sites/simple_cms
$ rake db:migrate
==  AlterUsers: migrating =====================================================
-- rename_table("users", "admin_users")
rake aborted!
An error has occurred, all later migrations canceled:

Mysql2::Error: Can't find file: './simple_cms_development/users.frm' (errno: 2 - No such file or directory): RENAME TABLE `users` TO `admin_users`/Users/gymmilo/Sites/simple_cms/db/migrate/20130927112013_alter_users.rb:3:in `change'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

---

Answer 1

您可以使用以下命令将数据库重置回原始状态并再次运行迁移。

rake db:reset

Answer 2

如果您的数据库来自生产数据库，您可以将其转储到本地计算机并运行 rake db:migrate。

如果只是一个测试数据库，运行“rake db:reset”，整个数据库会被刷新，所有的迁移任务都会被一一执行。