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From "Uwe Schindler" <...@thetaphi.de>
Subject RE: Alternative for WildcardQuery with leading *
Date Fri, 07 Dec 2012 09:34:25 GMT
In general, you seem to need decomposing...: vacancyplan -> tokenized to -> vacancyplan,
vacancy, plan. Wildcards are in general not really a replacement for correct text analysis
on the indexing side. Unfortunately, decomposing is a hard task, but there are dictionary-based
algorithms for e.g. German.

About the question with wildcards: If you really need a wildcard  in front, the common use
case is to also index all terms in backwards order. E.g. Solr does this with ReverseWildCardTokenFilter,
which indexes all terms forward and also in reverse order with some extra "marker-prefix"
on the reverse terms (to be able to differentiate between forwards and backwards terms in
the same field - of course, you could also index the reverse terms into an extra field). The
query parser then automatically produces a simple PrefixQuery with a transformed query term
(so it queries the magic extra reverse terms with a prefix).

Uwe

-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: uwe@thetaphi.de


> -----Original Message-----
> From: Clemens Wyss DEV [mailto:clemensdev@mysign.ch]
> Sent: Friday, December 07, 2012 10:16 AM
> To: java-user@lucene.apache.org
> Subject: Alternative for WildcardQuery with leading *
> 
> In order to provide suggestions our query also includes a "WildcardQuery
> with a leading *", which, of course, has a HUGE performance impact :-(
> 
> E.g.
> Say we have indexed "vacancyplan", then if a user typed "plan" he should
> also be offered "vacancyplan" ...
> 
> How can this feature be implemented without WcQwl* ?
> 
> Any help appreciated
> - Clemens
> 
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