ruby-on-rails - Rails 3，迁移在本地有效，在 Heroku 中不起作用？

Question

我最近发布了 this question

在本地工作，我选择的答案是正确的，这里是我主要使用的迁移:

class ChangeColumnToUsers < ActiveRecord::Migration
  def self.up
    change_column :users, :created_at, :datetime

  end

  def self.down
    change_column :users, :created_at, :string
  end
end

运行 heroku rake db:migrate 后，我收到此错误:

rake aborted!
An error has occurred, this and all later migrations canceled:

PGError: ERROR:  column "deadline" cannot be cast to type "date"
: ALTER TABLE "tasks" ALTER COLUMN "deadline" TYPE date

(See full trace by running task with --trace)
(in /disk1/home/slugs/18c5c920-2e22-40f5-8d6a-b20a0fc5d7ba/mnt)
==  ChangeColumnToUsers: migrating ============================================
-- change_column(:users, :created_at, :datetime)

有什么想法吗？

Answer 1

这是我在 SO 上找到的解决方法!

How do I change column type in Heroku?