使用数据映射器进行迁移

发布于 2025-01-08 17:18:26 字数 406 浏览 4 评论 0原文

我需要向我的用户模型添加另一列（电子邮件）。我不想修改 MySql 数据库中的现有数据。我该怎么做呢？

下面是我原始模型类的代码，我正在使用 Sinatra。提前致谢。

require 'rubygems'
require 'data_mapper'

DataMapper.setup(:default,'mysql://root@localhost/database')

class User
  include DataMapper::Resource
  property :id,              Serial
  property :name,            String, :unique=>true, :required=>true
end

DataMapper.finalize

原文

I need to add another column (email) to my User model. I do not wish to modify the existing data in MySql database. How should I do that?

Below is code of my original model class, and I am using Sinatra. Thanks in advance.

require 'rubygems'
require 'data_mapper'

DataMapper.setup(:default,'mysql://root@localhost/database')

class User
  include DataMapper::Resource
  property :id,              Serial
  property :name,            String, :unique=>true, :required=>true
end

DataMapper.finalize

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羁拥 2025-01-15 17:18:26

对于添加新列之类的简单操作，您可以修改模型，然后调用 auto_upgrade!，如下所示：

require 'rubygems'
require 'data_mapper'

class User
  include DataMapper::Resource
  property :id,              Serial
  property :name,            String, :unique=>true, :required=>true
  property :email,           String, :unique=>true, :required=>true
end

DataMapper.finalize
DataMapper::Logger.new(STDOUT,  :debug)
DataMapper.setup(:default,'mysql://root@localhost/database')
DataMapper.auto_upgrade!

请注意，我更改了调用 setup 的位置，以便 SQL日志是在连接建立之前创建的。这里的 SQL 日志包括以下行：

ALTER TABLE `users` ADD COLUMN `email` VARCHAR(50) NOT NULL

我相信它可以满足您的要求，而无需更改现有数据。但请注意，如果您想要更改列的功能（例如，更改字段的大小），则此操作将不起作用。 DataMapper 不会检查此类更改。

For simple things like adding a new column, you can modify your model and then call auto_upgrade!, like this:

require 'rubygems'
require 'data_mapper'

class User
  include DataMapper::Resource
  property :id,              Serial
  property :name,            String, :unique=>true, :required=>true
  property :email,           String, :unique=>true, :required=>true
end

DataMapper.finalize
DataMapper::Logger.new(STDOUT,  :debug)
DataMapper.setup(:default,'mysql://root@localhost/database')
DataMapper.auto_upgrade!

Notice that I changed where setup is called, so that an SQL log is created before the connection is set up. Here the SQL log includes the following line:

ALTER TABLE `users` ADD COLUMN `email` VARCHAR(50) NOT NULL

Which I believe does what you want, without altering existing data. Notice, however, that if you wanted to change the features of a column (e.g., changing the size of fields), this wouldn't work. DataMapper doesn't check for that kind of change.

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