所需文件
- active_support/benchmarkable
- active_support/dependencies
- active_support/descendants_tracker
- active_support/time
- active_support/core_ext/class/subclasses
- active_record/log_subscriber
- active_record/explain_subscriber
- active_record/relation/delegation
- active_record/attributes
- active_record/type_caster
- active_record/database_configurations
命名空间