[Zope] How to search a whole sub-tree?

Hi Zopers, I'm a newbie in this great zope world, and I've got a question that I'm sure is trivial: Situation: I have some folders that make up a catalog, and inside these folder there are other sub-folders and products. Problem: How can I find the products that match a particular criteria (eg. price<1000)? I know about ZCatalog, but do I have to refresh the index every time I change a price? Or do I have to traverse the whole catalog tree (deep first search, or similar algorithms)? I really hope there's a better way to do that. I'm still stuck in the relational database kind of thinking, this OO database is new to me. But "select * from prod where price<1000" would be nice. Nothing that easy with zope? Thanks in advance |G|