Stream helpers .flatMap should support recursion #509
Description
I believe it's currently impossible to paginate the equivalent of a Recursive CTE. For example, if you have a tree of messages which are replies to other messages, so each message has an optional parent pointer, can you do a paginated traversal of the tree? I don't think so. For one thing, the index keys of a QueryStream are currently always the same length.
Maybe we could just lift the restriction that all index keys are the same length, and then flatMap would be able to do the recursion?