[Xapian-devel] adaptive query scoring

[Olly Betts]

On Tue, May 16, 2006 at 05:43:07PM +0100, Richard Boulton wrote:
> I personally suspect that just adding entries to the RSet based on
> adaptive-terms won't give a particularly useful improvement (unless
> you often have searches with a large number of terms).  You'd probably
> have to do an autoexpand to add terms to the query based on the RSet,
> rather than just rely on the ranking from the RSet.

I suspect you're right - simply marking documents as relevant generally
has a fairly subtle effect on the ranking.

> > Yep, this sounds workable.
> > Does the ANDMAYBE operator add much overhead to queries?  Would it be
> > faster to just use the OR operator?  If a result matches the XCLICK*
> > term, it _must_ also match the original term.
> 
> In general, ANDMAYBE is likely to be more efficient than OR, because it
> allows faster skipping through the posting lists (and hence less I/O).  In
> this particular case, because of the condition you list, it should be
> equivalent to OR.  I'd be very surprised if it was less efficient.

I said ANDMAYBE because I suspected it might be a little more efficient
than OR, though I've not actually checked it through.

I don't believe it can be less efficient.  It's giving the matcher more
information (that the first term has to match) and the matcher can
potentially make use of that sort of information.

Cheers,
    Olly