rewrite turns
    foo*
into
   food  foot football ...

etc. Those variant terms are found by looking in the index, hence the need for 
the IndexReader.
Searcher calls rewrite on queries to do this - the highlighter just pre-empts 
this conversion and sneaks a peek at the terms generated so it can do its job 
more efficiently.



----- Original Message ----
From: Helmut Jarausch <[EMAIL PROTECTED]>
To: java-user@lucene.apache.org
Sent: Thursday, 13 December, 2007 11:40:01 AM
Subject: Query.rewrite - help me to understand it

Hi,

since I need highlighting, I need to 'rewrite' a query.
Query.rewrite  takes an object of type IndexReader

But what for?

As I understand it, rewrite transforms a possibly complicated
query into an simplified (internal?) form which is (unfortunately)
needed by QueryScorer which is in turn need by Highlighter.

What does Query.rewrite do and why does it need access to the
index?

Many thanks for an explanation,
Helmut.

-- 
Helmut Jarausch

Lehrstuhl fuer Numerische Mathematik
RWTH - Aachen University
D 52056 Aachen, Germany

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