使用模型延迟加载/缓存SQL查询结果

I'm developing a system (with Rails 2.3.2, Ruby 1.8.7-p72) that has a sizable reporting component. In order to improve performance, I've created a Report model to archive old reports. The idea is that if a matching report already exists for an arbitrary set of conditions then use it, otherwise generate the report and save the results.I'm developing a system (with Rails 2.3.2, Ruby