Hi,
> Hi,
> I'm trying to get the terms that match a certain RegexpQuery. My (naive)
> approach:
>
> 1. Create a RegexpQuery from the queryString (e.g. "abc.*"):
> Query q = new RegexpQuery(new Term("text", queryString));
>
> 2. Rewrite the Query using the IndexReader reader:
> q = q.rewrite(reader);
This works for this query, but in general you have to rewrite until it is
completely rewritten: A while loop that exits when the result of the rewrite is
identical to the original query. IndexSearcher.rewrite() does this for you.
> 3. Write the terms into a previously initialized empty set terms:
> Set<Term> terms = new HashSet<>();
> q.extractTerms(terms);
Set the rewrite method to e.g. SCORING_BOOLEAN_QUERY_REWRITE, then this should
work (after rewrite your query is a BooleanQuery, which supports
extractTerms()).
> However, this results in an empty set. I believe this is due to the fact that
> the
> rewritten query is a ConstantScoreQuery object;
> q.extractTerms(terms) does not yield any terms anyway. q.getQuery()
> returns null however; according to the documentation, this should happen
> when it wraps a filter which it does not, supposedly.
It wraps a filter: MultiTermQueryWrapperFilter
> This is Lucene 4.0. Any hints?
> Thanks!
> Carsten
>
>
> --
> Institut für Deutsche Sprache | http://www.ids-mannheim.de
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