Xapian devel - Mar 2010 - How the matcher knows when to prune and decay

Hi all, I have a question about Xapian internals, and since I don't speak
enough C++ to find out the answer from the source code, I thought I'd ask
here.

Since Xapian can prune or mutate the matching tree based on the largest possible
future score from the branch, I assumed Xapian stored postings in decreasing
order of frequency/weight/whatever. But recently I found some documentation that
said Xapian stores postings in document order.

So I'm wondering, how does the matcher know the maximum score of the rest of
the postings in a branch?

Thanks for your time!

Matt

On Tue, Mar 02, 2010 at 10:55:24PM -0500, Matt Chaput
wrote:
> So I'm wondering, how does the matcher know the maximum score of the
rest of
> the postings in a branch?
It asks the subtree for its maximum score, which the subtree calculates
recursively.

That maximum can decrease during the matching process - for example, when a
child of OP_OR reaches its end.

Cheers,
    Olly