我正在尝试使用postgresql 设置新的 Rails 5应用程序（红宝石2.3.1，rails 5.0.0.rc1），设计gems，rails db:seed由于以下错误，它无法运行：
PG::UndefinedTable: ERROR: relation "application_records" does not exist
LINE 8: WHERE a.attrelid = '"application_records"'::r...
^
/Users//.rvm/gems/ruby-2.3.1@rails5.0/gems/activerecord-5.0.0.rc1/lib/active_record/connection_adapters/postgresql/database_statements.rb:88:in `async_exec'
/Users/foo/.rvm/gems/ruby-2.3.1@rails5.0/gems/activerecord-5.0.0.rc1/lib/active_record/connection_adapters/postgresql/database_statements.rb:88:in `block in query'
/Users/foo/.rvm/gems/ruby-2.3.1@rails5.0/gems/activerecord-5.0.0.rc1/lib/active_record/connection_adapters/abstract_adapter.rb:566:in `block in log'
/Users/foo/.rvm/gems/ruby-2.3.1@rails5.0/gems/activesupport-5.0.0.rc1/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
/Users/foo/.rvm/gems/ruby-2.3.1@rails5.0/gems/activerecord-5.0.0.rc1/lib/active_record/connection_adapters/abstract_adapter.rb:560:in `log'
/Users/foo/.rvm/gems/ruby-2.3.1@rails5.0/gems/activerecord-5.0.0.rc1/lib/active_record/connection_adapters/postgresql/database_statements.rb:87:in `query'
/Users/foo/.rvm/gems/ruby-2.3.1@rails5.0/gems/activerecord-5.0.0.rc1/lib/active_record/connection_adapters/postgresql_adapter.rb:739:in `column_definitions'
/Users/foo/.rvm/gems/ruby-2.3.1@rails5.0/gems/activerecord-5.0.0.rc1/lib/active_record/connection_adapters/postgresql/schema_statements.rb:227:in `columns'
经过大量的搜索之后，我意识到这与Rails 5中ApplicationRecord基类的更改有关。显然没有调用任何表application_records，因此active_support不应查找该表。我已经检查过该app/models/application_record.rb内容并具有正确的内容。此外，用户模型（这是当前我的应用程序中唯一的模型）按预期扩展了ApplicationRecord：
class User < ApplicationRecord
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable,
:recoverable, :rememberable, :trackable, :validatable
end
rails db: migrate运行正常，但因 …