因此,如果此迁移导致任何错误,我希望能够恢复/rake db:rollback。
代码:
class ChangeUidToPrimaryKey < ActiveRecord::Migration
def change
execute ALTER TABLE "users" DROP CONSTRAINT "users_pkey".
execute ALTER TABLE "users" ADD PRIMARY KEY "uid"
end
end
在这种情况下,我可以添加什么向下/可逆代码来使 rake db:rollback 工作?
最佳答案
您可以执行以下操作,即如果您需要恢复,请在 email
上保留唯一索引。
class ChangeUidToPrimaryKey < ActiveRecord::Migration
def self.up
execute "alter table users add constraint unique_users_email unique(email)"
execute "ALTER TABLE users DROP CONSTRAINT users_pkey"
execute "ALTER TABLE users ADD PRIMARY KEY (uid)"
end
def self.down
execute "ALTER TABLE users DROP CONSTRAINT users_pkey"
execute "ALTER TABLE users DROP CONSTRAINT unique_users_email"
execute "ALTER TABLE users ADD PRIMARY KEY (email)"
end
end
关于ruby-on-rails - 我如何在此迁移中编写向下或可逆函数?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18159314/