module ActiveRecord

ActiveRecord resources:

lib/active_record/connection_adapters/mysql2_adapter.rb
lib/active_record/connection_adapters/abstract_mysql_adapter.rb
lib/active_record/schema_dumper.rb

and a few other files.

ActiveRecord resources:

lib/active_record/attributes.rb
lib/active_record/type/value.rb
lib/active_record/type/mutable.rb