[Xapian-discuss] QueryParser (I think) question

[Olly Betts]

On Wed, May 23, 2007 at 09:26:05AM +0200, Andreas Marienborg wrote:
> On May 22, 2007, at 10:01 PM, Richard Boulton wrote:
> >Firstly, I should note that I don't get the same behaviour as you  
> >here (with Xapian 1.0.0, and the standard options for parse_query 
> >()): I'm guessing from your output that you're using a Xapian 0.9  
> >release. Upgrading might help a bit, but the handling isn't perfect  
> >even in 1.0.0, sadly: query parsers are incredibly hard to get  
> >right for all cases.
> 
> Yes, but I am unable to find Search::Xapian (perl-modules) for 1.0 on  
> cpan. Is there anywhere else I might obtain them?

I'm working on updating Search::Xapian for 1.0.0, but it's not quite
ready yet - I still need to finish wrapping the new TermGenerator class.

Here's a snapshot of the current state.  I wouldn't advise using this in
a production system yet, but it should be fine for testing.

http://oligarchy.co.uk/xapian/patches/Search-Xapian-1.0.0.0.tar.gz

> Query: (brukervennlighet) AND (source:1 OR source:2)
> unmodified query: Xapian::Query((brukervennlighet:(pos=1) AND (S1 OR  
> S2)))
> [...]

I'm not sure it's especially interesting exactly why these examples
parse as they do.  Essentially, those that "work" do so by coincidence.

The grammar needs sorting out to make this work properly.  We also
need to decide what something like this should do:

    brukervennlighet OR source:1

The problem with the "obvious" interpretation is how the ranking should
work.  We could just treat source:1 as a probabilistic term.  Xapian
doesn't really distinguish at the term level so this would work, but
does that make sense for a term prefix we were told was a boolean
filter?

> When searching I do
>     my $query_obj=$self->qp->parse_query( $processed_query );
> so I don't think I am setting any flags.

You're implicitly setting the default flags, which are the same for
Perl and C++ (though the Perl wrappers currently hardcode them as `7'
which is just asking for problems in the future, as well as being an
obscure magic value).

Cheers,
    Olly