没有迁移表的 Rails STI 模型答案

【问题标题】：Rails STI model without a table on migrations没有迁移表的 Rails STI 模型
【发布时间】：2013-03-23 08:15:15
【问题描述】：

我有一个模型，比如说User，还有一个模型Admin，它继承自User。我在lib 文件夹中有一些使用这两个模型的代码。但是，如果我安装一个新数据库并尝试运行迁移 rails 崩溃说没有像 User 这样的模型。是否有绕过此错误的最佳做法？

`Mysql2::Error: Table 'testing_interface_development.users' doesn't exist: SHOW FULL FIELDS FROM `users`
/home/arthurborisow/Programming/my_project/test_interface/lib/active_record/timed_out_queries_hotfix.rb:9:in `query'
/home/arthurborisow/Programming/my_project/test_interface/lib/active_record/timed_out_queries_hotfix.rb:9:in `query_with_reconnect'
/home/arthurborisow/Programming/my_project/test_interface/lib/active_record/timed_out_queries_hotfix.rb:31:in `block in execute'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/connection_adapters/abstract_adapter.rb:280:in `block in log'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activesupport-3.2.11/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/connection_adapters/abstract_adapter.rb:275:in `log'
/home/arthurborisow/Programming/my_project/test_interface/lib/active_record/timed_out_queries_hotfix.rb:31:in `execute'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:259:in `execute_and_free'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:426:in `columns'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/connection_adapters/schema_cache.rb:12:in `block in initialize'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/model_schema.rb:228:in `yield'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/model_schema.rb:228:in `columns'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/model_schema.rb:237:in `columns_hash'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/inheritance.rb:19:in `descends_from_active_record?'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/inheritance.rb:25:in `finder_needs_type_condition?'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/base.rb:455:in `relation'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/scoping/named.rb:37:in `scoped'
/home/arthurborisow/.rvm/gems/ruby-1.9.3-p362-railsexpress@test_interface_install/gems/activerecord-3.2.11/lib/active_record/querying.rb:9:in `where'
/home/arthurborisow/Programming/my_project/test_interface/app/models/admin.rb:15:in `<class:Admin>'
/home/arthurborisow/Programming/my_project/test_interface/app/models/admin.rb:1:in `<top (required)>'`

【问题讨论】：

您能否发布确切的错误，将--trace 传递给rake？
你的项目中lib/active_record/timed_out_queries_hotfix.rb的内容是什么？根据回溯，这似乎是错误的根源

标签： ruby-on-rails ruby-on-rails-3 activerecord model

【解决方案1】：

当设置一个全新的数据库（而不是升级现有的）时，最好使用rake db:setup 加载schema.rb 文件，而不是连续运行每个迁移。这个问题很好地解释了各种 db Rake 任务：

Difference between rake db:migrate db:reset and db:schema:load

【讨论】：

db:schema:load也存在同样的问题

【解决方案2】：

   rake db:setup

也是最好的选择，

您还可以使用以下命令指定要迁移的迁移版本：

rake db:migrate:up VERSION=20080906120000

【讨论】：