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

[aaa@simplesky.com]

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|