在第一次迁移后更改字段名称时，Rails db 迁移中止错误

Question

我偶然命名了 add_column :users, :confirmed_at(confirmation_at), :datetime。所以我把它改成了合适的字段名:(confirmed_at)

然后我在命令行中输入：rake db:rollback。由于某种原因，它被中止了，但首先是我的 Rails db 迁移文件代码：

class AddConfirmableToDevise < ActiveRecord::Migration
  def up
    add_column :users, :confirmation_token, :string
    add_column :users, :confirmed_at, :datetime
    add_column :users, :confirmation_sent_at, :datetime

    add_index :users, :confirmation_token, unique: true
  end

  def down
    remove_column :users, :confirmation_token, :confirmed_at, :confirmation_sent_at
  end
end

迁移后出错：

tzurch:~/workspace (gravitar) $ rake db:migrate:redo

#the error that came up below
_________________________________________________
== 20160902201448 AddFullnameToUser: reverting ================================

-- remove_column(:users, :fullname, :string)

-> 0.0207s

== 20160902201448 AddFullnameToUser: reverted (0.0284s) =======================

== 20160902201448 AddFullnameToUser: migrating ================================

-- add_column(:users, :fullname, :string)

-> 0.0008s

== 20160902201448 AddFullnameToUser: migrated (0.0009s) =======================

== 20160913221959 AddConfirmableToDevise: migrating ===========================

-- add_column(:users, :confirmation_token, :string)

-> 0.0009s

-- add_column(:users, :confirmed_at, :datetime)

-> 0.0005s

-- add_column(:users, :confirmation_sent_at, :datetime)

rake aborted!

StandardError: An error has occurred, this and all later migrations canceled:

SQLite3::SQLException: duplicate column name: confirmation_sent_at: ALTER TABLE "users" ADD "confirmation_sent_at" datetime:

Answer 1

我想你已经在 db 的这个表中有confirmation_sent_at 字段

Answer 2

这里的问题是你用来删除列的语法是错误的。

正确的语法是remove_column

remove_column(table_name, column_name, type = nil, options = {})

更改向下迁移

class AddConfirmableToDevise < ActiveRecord::Migration
  def up
    add_column :users, :confirmation_token, :string
    add_column :users, :confirmed_at, :datetime
    add_column :users, :confirmation_sent_at, :datetime

    add_index :users, :confirmation_token, unique: true
  end

  def down
    remove_column :users, :confirmation_token
    remove_column :users, :confirmed_at
    remove_column :users, :confirmation_sent_at

    remove_index :users, :confirmation_token
  end
end

或者完全删除down迁移并将up替换为change，rails会弄清楚如何回滚：

class AddConfirmableToDevise < ActiveRecord::Migration
  def change
    add_column :users, :confirmation_token, :string
    add_column :users, :confirmed_at, :datetime
    add_column :users, :confirmation_sent_at, :datetime

    add_index :users, :confirmation_token, unique: true
  end
end