Are there any Ruby ORMs which use cursors or smart fetch?

I'm looking for a Ruby ORM to replace ActiveRecord. I've been looking at Sequel and DataMapper. They look pretty good however none of them seems to do the basic: not loading everything in memory when you don't need it.

I mean I've tried the following (or equivalent) on ActiveRecord and Sequel on table with lots of rows:

 posts.each { |p| puts p }

Both of them go crazy on memory. They seem to load everything in memory rather than fetching stuff when needed. I used the find_in_batches in ActiveRecord, but it's not an acceptable solution:

1. ActiveRecord is not an acceptable solution because we had too many problems with it.

2. Why should my code be aware of a paging mechanism? I'm happy to configure somewhere the size of the page but that's it. With find_in_batches you need to do something like:

   post.find_in_batches { |batch| batch.each { |p| puts p } }

But that should be transparent.

So is there somewhere a reliable Ruby ORM which does the fetch properly?

Update:

As Sergio mentioned, in Rails 3 you can use find_each which exactly what I want. However as ActiveRecord is not an option, except if someone can really convince me to use it, the questions are:

1. Which ORMs support the equivalent of find_each?
2. How to do it?
3. Why do we need a find_each, while find should do it, shouldn't it?