即使在完全运行迁移后，Rake 也会中止

Question

当我生成一个新的迁移并通过上下检查时，我得到“rake aborted！”最后当我下楼时，虽然它运行了所有的迁移。并且在上迁移过程中没有任何问题，一切都很顺利。谁能告诉我为什么会这样？

 $ rake db:migrate VERSION= 20140217090240
==  CreateSections: reverting =================================================
-- drop_table(:sections)    -> 0.0050s
==  CreateSections: reverted (0.0060s) ========================================

==  CreatePages: reverting ====================================================
-- drop_table(:pages)    -> 0.0030s
==  CreatePages: reverted (0.0040s) ===========================================

==  CreateSubjects: reverting =================================================
-- drop_table(:subjects)    -> 0.0030s
==  CreateSubjects: reverted (0.0230s) ========================================

==  AlterUsers: reverting =====================================================
-- remove_index("admin_users", "username")    -> 0.0180s
-- rename_column("admin_users", "hashed_password", "password")    -> 0.0160s
-- change_column("admin_users", "email", :string, {:default=>"", :null=>false})    -> 0.0110s
-- remove_column("admin_users", "username")    -> 0.0110s
-- rename_table("admin_users", "users")    -> 0.0030s
==  AlterUsers: reverted (0.0680s) ============================================

==  CreateUsers: reverting ====================================================
-- drop_table(:users)    -> 0.0040s
==  CreateUsers: reverted (0.0040s) ===========================================

rake aborted! Don't know how to build task '20140217090240'

(See full trace by running task with --trace)

class CreateUsers < ActiveRecord::Migration
  def up
    create_table :users do |t|
      t.string "first_name", :limit => 25
      t.string "last_name", :limit => 50
      t.string "email", :default => "", :null => false
      t.string "password", :limit => 40     
      t.timestamps
    end
  end

  def down
    drop_table :users
  end
end

Answer 1

使用

开始迁移

  rake db:migrate:up VERSION=version number of migration

为了向下迁移运行

 rake db:migrate:down VERSION=version number of migration

Answer 2

您的“CreateUsers”迁移文件包含错误。请先观察用户创建文件。它可能具有一些依赖性，例如您在创建迁移中添加了某些用户角色，但角色表未在用户表之前创建。如果您将“CreateUsers”迁移文件粘贴到某处，然后将链接粘贴到此处，就很容易找出问题所在。