これは、active_record/connection_adapters/abstract/quoting.rb の def quote(value, column = nil) # records are quoted as their primary key return value.quoted_id if value.respond_to?(:quoted_id) : かな。
で、AR::Base に戻って def quoted_id #:nodoc: quote_value(id, column_for_attribute(self.class.primary_key)) end
