[Xapian-discuss] ADJ Performance

[Olly Betts]

On Mon, Sep 10, 2012 at 11:30:45PM +0100, Olly Betts wrote:
> On Mon, Sep 10, 2012 at 02:16:59PM +0800, ???? wrote:
> > Xapian:1.2.5
> > 
> > About 2.3GB of database files and 250,000 documents.
> > 
> > When I use ADJ mode just like "how ADJ/1 much", It cost about 15s. So my
> > question is how to improve performance.
> 
> This is essentially the issue which ticket 394 is about:
> 
> http://trac.xapian.org/ticket/394
> 
> The patch there only addresses exact ordered phrases, so will help ADJ/1
> but not ADJ/2 or more, or NEAR, but the same idea will work for other
> queries which use positional information.
> 
> Coincidentally, I'm currently working on tidying up this patch and
> getting it merged to trunk.

While working on this, I noticed a simpler optimisation, which is more
widely applicable (though probably not as effective).

Could you try this patch and see how much difference it makes to your
test case:

http://trac.xapian.org/attachment/ticket/394/positional-query-weight-check-first-1.2.patch

Cheers,
    Olly