[Xapian-discuss] Simulating Fields

[Olly Betts]

On Sun, May 03, 2009 at 10:04:03PM -0400, Luis Alberto Zarrabeitia Gomez wrote:
> 
> Quoting James Aylett <james-xapian at tartarus.org>:
> 
> > You can use the QueryParser for this; set a term prefix before parsing
> > the query, for instance.
> 
> I tried to do this (qp is a QueryParser instance, with the same stemmer)
> 
> ===
>   qp.set_stemming_strategy(xapian.QueryParser.STEM_SOME)
>   qp.add_boolean_prefix("realtitle",'XTITLE')
>   qp.add_prefix("title","XTITLE")
> ===

I'm not sure what you think "realtitle" is going to be useful for.  It
doesn't generally make sense to have the same term prefix generated by
both boolean and probabilistic prefixes.

> but then... how do I construct the query?
> 
>   title:Sex and the City
> 
> produces the query:
>   Xapian::Query((XTITLEsex:(pos=1) OR Zand:(pos=2) OR Zthe:(pos=3) OR city:(pos=4)))
> 
> (i.e, only "sex" in the title), while
> 
>   title:'Sex and the City'

If you want a phrase, the syntax is double quotes:

title:"Sex and the City"

If you want to apply the prefix to all terms in a subexpression, use
brackets:

title:(Sex and the City)

Note that the syntax supported by the QueryParser is described here:

http://xapian.org/docs/queryparser.html

> > Not that if you're matching on exact titles,
> > you probably want a phrase search (or, if you're not doing anything
> > else, possibly to construct the term as XTITLE<title> and match it as
> > a single (boolean) term, without using the QueryParser at all).
> 
> I guess that'd mean that during the indexing, I would have to use the whole
> title as a single term? (just to be clear), instead of
> 'indexer.index_text(page.title,1,"XTITLE")'. What function should I call, then?
> Could you provide me an example?

    document.add_term("XTITLE" + page.title)

I'm not sure I'd recommend this approach though - there's a limit of
about 240 bytes on the length of terms.

Cheers,
    Olly