按日期范围过滤Sphinx搜索结果

I have Widget.title, Widget.publish_ at, and Widget.unpublish_ at. It's a rails app with thinking_sphinx running, indexing once a night. I want to find all Widgets that have 'foo' in the title, and are published (publish _at < Time.now, unpublish _at > Time.now). I have Widget.title, Widget.publish_ at, and Wi