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From "Karl Wettin (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-522) SpanFuzzyQuery
Date Fri, 17 Mar 2006 22:12:01 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-522?page=comments#action_12370896 ] 

Karl Wettin commented on LUCENE-522:
------------------------------------

I found some bugs. 

If there are no alternatives it generates a bad query. I'll fix that.

If the index is empty, it generates an even worse query. Might be a FuzzyQuery problem though.

Also it throws nullpointer if you do a toString() prior to rewriting the query. Perhaps thats
the way it is? Didn't check it out. Just reporting before I forget about it.

> SpanFuzzyQuery
> --------------
>
>          Key: LUCENE-522
>          URL: http://issues.apache.org/jira/browse/LUCENE-522
>      Project: Lucene - Java
>         Type: New Feature
>   Components: Search
>     Versions: 1.9
>     Reporter: Karl Wettin
>     Priority: Minor

>
> This is my SpanFuzzyQuery. It is released under the Apache licensence. Just paste it
in.
> package se.snigel.lucene;
> import org.apache.lucene.index.IndexReader;
> import org.apache.lucene.index.Term;
> import org.apache.lucene.search.*;
> import org.apache.lucene.search.spans.SpanOrQuery;
> import org.apache.lucene.search.spans.SpanQuery;
> import org.apache.lucene.search.spans.SpanTermQuery;
> import org.apache.lucene.search.spans.Spans;
> import java.io.IOException;
> import java.util.Collection;
> import java.util.LinkedList;
> /**
>  * @author Karl Wettin <kalle@snigel.net>
>  */
> public class SpanFuzzyQuery extends SpanQuery {
>     public final static float defaultMinSimilarity = 0.7f;
>     public final static int defaultPrefixLength = 0;
>     private final Term term;
>     private final float minimumSimilarity;
>     private final int prefixLength;
>     private BooleanQuery rewrittenFuzzyQuery;
>     public SpanFuzzyQuery(Term term) {
>         this(term, defaultMinSimilarity, defaultPrefixLength);
>     }
>     public SpanFuzzyQuery(Term term, float minimumSimilarity, int prefixLength) {
>         this.term = term;
>         this.minimumSimilarity = minimumSimilarity;
>         this.prefixLength = prefixLength;
>         if (minimumSimilarity >= 1.0f) {
>             throw new IllegalArgumentException("minimumSimilarity >= 1");
>         } else if (minimumSimilarity < 0.0f) {
>             throw new IllegalArgumentException("minimumSimilarity < 0");
>         }
>         if (prefixLength < 0) {
>             throw new IllegalArgumentException("prefixLength < 0");
>         }
>     }
>     public Query rewrite(IndexReader reader) throws IOException {
>         FuzzyQuery fuzzyQuery = new FuzzyQuery(term, minimumSimilarity, prefixLength);
>         rewrittenFuzzyQuery = (BooleanQuery) fuzzyQuery.rewrite(reader);
>         BooleanClause[] clauses = rewrittenFuzzyQuery.getClauses();
>         SpanQuery[] spanQueries = new SpanQuery[clauses.length];
>         for (int i = 0; i < clauses.length; i++) {
>             BooleanClause clause = clauses[i];
>             TermQuery termQuery = (TermQuery) clause.getQuery();
>             spanQueries[i] = new SpanTermQuery(termQuery.getTerm());
>             spanQueries[i].setBoost(termQuery.getBoost());
>         }
>         SpanOrQuery query = new SpanOrQuery(spanQueries);
>         query.setBoost(fuzzyQuery.getBoost());
>         return query;
>     }
>     /** Expert: Returns the matches for this query in an index.  Used internally
>      * to search for spans. */
>     public Spans getSpans(IndexReader reader) throws IOException {
>         throw new UnsupportedOperationException("Query should have been rewritten");
>     }
>     /** Returns the name of the field matched by this query.*/
>     public String getField() {
>         return term.field();
>     }
>     /** Returns a collection of all terms matched by this query.*/
>     public Collection getTerms() {
>         if (rewrittenFuzzyQuery == null) {
>             throw new RuntimeException("Query must be rewritten prior to calling getTerms()!");
>         } else {
>             LinkedList<Term> terms = new LinkedList<Term>();
>             BooleanClause[] clauses = rewrittenFuzzyQuery.getClauses();
>             for (int i = 0; i < clauses.length; i++) {
>                 BooleanClause clause = clauses[i];
>                 TermQuery termQuery = (TermQuery) clause.getQuery();
>                 terms.add(termQuery.getTerm());
>             }
>             return terms;
>         }
>     }
>     /** Prints a query to a string, with <code>field</code> as the default
field
>      * for terms.  <p>The representation used is one that is supposed to be readable
>      * by {@link org.apache.lucene.queryParser.QueryParser QueryParser}. However,
>      * there are the following limitations:
>      * <ul>
>      *  <li>If the query was created by the parser, the printed
>      *  representation may not be exactly what was parsed. For example,
>      *  characters that need to be escaped will be represented without
>      *  the required backslash.</li>
>      * <li>Some of the more complicated queries (e.g. span queries)
>      *  don't have a representation that can be parsed by QueryParser.</li>
>      * </ul>
>      */
>     public String toString(String field) {
>         return "spans(" + rewrittenFuzzyQuery.toString() + ")";
>     }
> }

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