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From "karl wetttin (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-522) SpanFuzzyQuery
Date Thu, 16 Mar 2006 22:33:58 GMT
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 wetttin
    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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