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From "John Wang" <john.w...@gmail.com>
Subject Re: Why Lucene has to rewrite queries prior to actual searching?
Date Mon, 07 Apr 2008 22:08:22 GMT
Other use is for custom Query objects to reboost or expand the user query
from information gathered from the indexreader at search time.
-John

On Mon, Apr 7, 2008 at 2:56 PM, Paul Elschot <paul.elschot@xs4all.nl> wrote:

> Itamar,
>
> Query rewrite replaces wildcards with terms available from
> the index. Usually that involves replacing a wildcard with a
> BooleanQuery that is an effective OR over the available
> terms while using a flat coordination factor, i.e. it does not
> matter how many of the available terms actually match
> a document, as long as at least one matches.
>
> For the required query parts (AND like), Scorer.skipTo()
> is used, and that could well be the filter mechanism you
> are referring to; have a look at the javadocs of Scorer,
> and, if necessary, at the actual code of ConjunctionScorer.
>
> Regards,
> Paul Elschot
>
>
>
>
>
> Op Monday 07 April 2008 23:13:09 schreef Itamar Syn-Hershko:
> > Hi all,
> >
> > Can someone from the experts here explain why Lucene has to get a
> > "rewritten" query for the Searcher - so Phrase or Wildcards queries
> > have to rewrite themselves into a "primitive" query, that is then
> > passed to Lucene to look for? I'm probably not familiar too much with
> > the internals of Lucene, but I'd imagine that if you can inflate a
> > query using wildcards via xxxxQuery sub classing, you could as easily
> > (?) have some sort of Filter mechanism during the search, so that
> > Lucene retrieves the Position vectors for all the terms that pass
> > that filter, instead of retrieving only the position data for
> > deterministic terms (with no wildcards etc.). If that was possible to
> > do somehow, it could greatly increase the searchability of Lucene
> > indices by using RegEx (without re-writing and getting the dreaded
> > MaxClauseCount error) and similar.
> >
> > Would love to hear some insights on this one.
> >
> > Itamar.
>
>
>
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