Question

我在生产模式下迁移数据库时遇到了一个奇怪的问题。初始rake db:migrate失败，错误“对象不缺少常量用户”，其中User是我的模型之一，在此迁移中可以像这样访问：

add_column :users, :feedbacks_count, :integer, :default => 0
    User.reset_column_information
    User.all.each do |u|
      u.update_attribute :feedbacks_count, u.feedbacks.length
    end
end

日志说明如下：

对象不会丢失常量用户！

/var/lib/gems/1.8/gems/activesupport-2.3.4/lib/active_support/dependencies.rb:417:in   `load_missing_constant'

/var/lib/gems/1.8/gems/activesupport-2.3.4/lib/active_support/dependencies.rb:80:in   `const_missing_not_from_s3_library'

/var/lib/gems/1.8/gems/aws-s3-0.6.2/lib/aws/s3/extensions.rb:206:in`const_missing'

/var/lib/gems/1.8/gems/activesupport-2.3.4/lib/active_support/dependencies.rb:92:in   `const_missing'

/var/lib/gems/1.8/gems/activesupport-2.3.4/lib/active_support/dependencies.rb:98:in   `发送“

/var/lib/gems/1.8/gems/activesupport-2.3.4/lib/active_support/dependencies.rb:98:in   `const_missing'

./分贝/迁移// 20100823185519_add_columns_for_counter_caches.rb：5：在   `up_without_benchmarks'

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:282:in   `发送“

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:282:in   `迁移'

/usr/lib/ruby/1.8/benchmark.rb:293:in   `衡量“

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:282:in   `迁移'

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:365:in   `的发送

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:365:in   `迁移'

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:486:in   `迁移'

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:562:in   `称之为“

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:562:in   `ddl_transaction'

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:485:in   `迁移'

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:472:in   `每个'

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:472:in   `迁移'

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:400:in   `向上“

/var/lib/gems/1.8/gems/activerecord-2.3.4/lib/active_record/migration.rb:383:in   `迁移'

/var/lib/gems/1.8/gems/rails-2.3.4/lib/tasks/databases.rake:116

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in`call'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in'execute'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in` each'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in'execute'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in`invoke_with_call_chain'

/usr/lib/ruby/1.8/monitor.rb:242:in   `同步'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in`invoke_with_call_chain'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in“invoke”

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in   `invoke_task'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in   `TOP_LEVEL'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in   `每个'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in   `TOP_LEVEL'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in   `standard_exception_handling'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in   `TOP_LEVEL'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in   `运行'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in   `standard_exception_handling'

/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in   `运行'

/var/lib/gems/1.8/gems/rake-0.8.7/bin/rake:31   / usr / bin / rake：19：在'load'

的/ usr /斌/耙：19

我读了很多文章，指的是“对象不缺少常量X”，其中问题主要是通过lazy_loading或访问插件来引用模型。在访问users表之前，在add_column之前要求'user.rb'或添加User.new并不能解决问题。

在发生故障之前访问用户模型也不会造成任何问题。

关于这个问题最奇怪的是，我在一天前将相同的代码迁移到另一台服务器，具有相同的设置和生产中，迁移运行没有任何问题。

任何帮助都会被贬低！

Answer 1

当然，我不应该要求用户模型，而是将User类添加到Migration by

class User < ActiveRecord::Base; end

这就是所有的事情。

还有待检查的是，为什么用户模型不为移民所知....

Answer 2

您的Amazon S3设置中的某些内容配置错误。你是否缺少配置目录中的S3配置文件？

生产中的rails迁移失败，“Object is not missing Constant User”

2 个答案: