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From "Pravin Shinde" <getpra...@gmail.com>
Subject Re: Leading wildcard query
Date Fri, 28 Jul 2006 10:27:11 GMT
Thanx for reply Miles
So, avoiding leading wildcard query was design decision
for sake of efficiency. Thanx for information.

On 7/28/06, Miles Barr <miles@magpie.net> wrote:
> Pravin Shinde wrote:
>
> > I am trying to use Leading wildcard query, but I am not able to do it.
> > Any query with leading wildcard is failing with lexical error.
> >
> > query = parser.parse( "*hi" )
> > JavaError: org.apache.lucene.queryParser.ParseException:
> > Lexical error at line 1, column 1.  Encountered: "*" (42), after : ""
> >
> >
> > I came across some documentation in Lucene FAQ which says
> >
> > http://wiki.apache.org/jakarta-lucene/LuceneFAQ#head-4d62118417eaef0dcb87f4370583f809848ea695
> >
> >
> > Note: Leading wildcards (e.g. *ook) are not supported by the
> > QueryParser (although Lucene could handle them -- see the comment in
> > QueryParser.jj to enable these kind of queries -- search for "OG: to
> > support prefix queries:").
> >
> > Is there any way I can do Leading wildchard query ?
>
>
> You could implement something, but it would have to be done differently
> to how wildcard queries are currently done. A wildcard query expands to
> match all possible tokens that match that pattern currently in the index
> (restricted to that field). I think the way the index is set up makes it
> possible to build this list when you know at least the first character.
> By starting with a * you need to get the complete list of tokens, then
> filter out those that don't match. I imagine this would be quite slow,
> hence why it's not in Lucene at the moment.
>
>
>
>
> Miles
>
>
>
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>


-- 
Regards,
Pravin Shinde

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