现有列的change_column_null [英] change_column_null for existing column

问题描述

我试图更改:profiles表上现有列:access_titles上布尔属性的nil可能性.该列之所以存在是因为进行了迁移:

I'm attempting to change the nil possibility of a boolean attribute on the existing column :access_titles on the :profiles table. That column exists because of this migration:

class AddAccessItemsToProfiles < ActiveRecord::Migration
  def self.up
    add_column :profiles, :access_items, :boolean, :default => true
  end

  def self.down
    remove_column :profiles, :access_items, :boolean, :default => nil
  end
end

要更改nil，我尝试像往常一样生成迁移:

To change nil, I tried generating a migration as I always have:

rails g migration ChangeColumnNull :profiles :access_items :null => false

但是那什么也没做，所以我做了一个独立的迁移:

But that did nothing, so I did a standalone migration:

rails g migration AddChangeColumnNullToAccessItems

在其中我添加了:

class AddChangeColumnNullToAccessItems < ActiveRecord::Migration
  def self.up
    change_column_null :profiles, :access_items, :boolean, false
  end

  def self.down
    change_column_null :profiles, :access_items, :boolean, true
  end
end

然后我运行了rake db:migrate，重新启动了服务器，未发现任何更改.所以我尝试了:

I then ran rake db:migrate, restarted my server and saw no changes. So I tried:

class AddChangeColumnNullToAccessItems < ActiveRecord::Migration
  def self.up
    change_column_null :profiles, :access_items, false
  end

  def self.down
    change_column_null :profiles, :access_items, true
  end
end

然后做同样的事情:rake db:migrate，重新启动服务器，没有任何改变.

Then did the same thing: rake db:migrate, restarted the server, and nothing changed.

我做错了什么?我希望只将:access_items的布尔值设为true和false，而不必转储数据库.

What am I doing wrong? I was hoping to only have the boolean value of :access_items be true and false without having to dump the database.

更新:尝试change_column_null :profiles, :access_items, false我遇到错误:

-- change_column_null(:profiles, :access_items, false)
rake aborted!
An error has occurred, this and all later migrations canceled:

PGError: ERROR:  column "access_items" contains null values
: ALTER TABLE "profiles" ALTER "access_items" SET NOT NULL

因此，根据以下建议，我必须在迁移中插入change_column_null :profiles, :access_items, false, true.

So, per the advice below I had to insert change_column_null :profiles, :access_items, false, true into my migration.

推荐答案

您可以使用:

change_column_null :profiles, :access_items, false, 1

第四个参数是可选的，它允许您设置列的默认值.当您在列中包含空值并将空值设置为false时，这是必需的.

The fourth parameter is optional and allows you to set the default value for the column. This is required when you have nulls in a column and you're setting the null value to false.

这篇关于现有列的change_column_null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！