raails 4.0.1中的column_types为nil

我正在尝试将Rails从4.0.0升级到4.0.2,但是4.0.1中引入的更改破坏了我的应用程序.

这是我看到的错误:

undefined method `[]' for nil:NilClass

activerecord (4.0.2) lib/active_record/attribute_methods/read.rb:86:in `block in read_attribute'
activerecord (4.0.2) lib/active_record/attribute_methods/read.rb:84:in `fetch'
activerecord (4.0.2) lib/active_record/attribute_methods/read.rb:84:in `read_attribute'
activerecord (4.0.2) lib/active_record/attribute_methods/read.rb:59:in `__temp__6696273747f5e616d656'
app/models/player.rb:20:in `short_name'

这是堆栈跟踪开始的应用程序代码:

# app/models/player.rb
def short_name
  self.class.where(first_name: first_name).where('id != ?', id).exists? ? name : first_name
end

这是出现问题的差异(和Rails上的提交):

diff -r activerecord-4.0.0/lib/active_record/attribute_methods/read.rb activerecord-4.0.1/lib/active_record/attribute_methods/read.rb

[snip]

80,86c85,92
<           column = @columns_hash.fetch(name) {
<             return @attributes.fetch(name) {
<               if name == 'id' && self.class.primary_key != name
<                 read_attribute(self.class.primary_key)
<               end
<             }
<           }
---
>           column = @column_types_override[name] if @column_types_override
>           column ||= @column_types[name]
> 
>           return @attributes.fetch(name) {
>             if name == 'id' && self.class.primary_key != name
>               read_attribute(self.class.primary_key)
>             end
>           } unless column

根据堆栈跟踪,@column_types是零,我无法弄清楚为什么.

我在控制台上没有这个问题,只有当我在服务器上运行时,无论是Thin via rails s(开发环境)还是Unicorn via foreman start(生产环境).当我部署到Heroku上的暂存时,它也会失败.我也有测试覆盖这个方法,他们通过了.

有谁知道@column_types应该设置在哪里以及为什么在这种情况下它是零？