de.unihildesheim.iw.lucene.query.TryExactTermsQuery.java Source code

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Here is the source code for de.unihildesheim.iw.lucene.query.TryExactTermsQuery.java

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/*
 * Copyright (C) 2014 Jens Bertram <code@jens-bertram.net>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package de.unihildesheim.iw.lucene.query;

import de.unihildesheim.iw.util.StringUtils;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.queryparser.classic.MultiFieldQueryParser;
import org.apache.lucene.queryparser.classic.ParseException;
import org.apache.lucene.queryparser.classic.QueryParser;
import org.apache.lucene.queryparser.classic.QueryParserBase;
import org.apache.lucene.search.BooleanClause;
import org.apache.lucene.search.BooleanClause.Occur;
import org.apache.lucene.search.BooleanQuery;
import org.jetbrains.annotations.NotNull;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * Query builder that tries to match all terms from a given query. A {@link
 * #relax()} method is provided to stepwise reduce the number of terms that must
 * match in a document. <br> Example: If a query "Lucene in action" is provided
 * at first all three terms must match. If {@link #relax()} was called only two
 * terms of the original query must match and so on.
 *
 * @author Jens Bertram
 */
public final class TryExactTermsQuery implements TermsProvidingQuery, RelaxableQuery {

    /**
     * Logger instance for this class.
     */
    private static final Logger LOG = LoggerFactory.getLogger(TryExactTermsQuery.class);

    /**
     * Final query object.
     */
    private final BooleanQuery query;

    /**
     * List of terms contained in the query (stopped, analyzed).
     */
    private final Collection<String> queryTerms;
    /**
     * List of unique terms contained in the query (stopped, analyzed).
     */
    private final Set<String> uniqueQueryTerms;

    /**
     * New instance using the supplied query.
     *
     * @param analyzer Query analyzer
     * @param queryStr Query string
     * @param fields Fields to query
     * @throws ParseException Thrown, if the query could not be parsed
     */
    public TryExactTermsQuery(@NotNull final Analyzer analyzer, @NotNull final String queryStr,
            @NotNull final String... fields) throws ParseException {
        if (fields.length == 0) {
            throw new IllegalArgumentException("Empty fields list.");
        }
        if (StringUtils.isStrippedEmpty(queryStr)) {
            throw new IllegalArgumentException("Empty query.");
        }

        this.queryTerms = QueryUtils.tokenizeQueryString(queryStr, analyzer);

        final QueryParser qParser = new MultiFieldQueryParser(fields, analyzer);

        this.query = new BooleanQuery();
        this.uniqueQueryTerms = new HashSet<>(this.queryTerms);
        for (final String term : this.uniqueQueryTerms) {
            @SuppressWarnings("ObjectAllocationInLoop")
            final BooleanClause bc = new BooleanClause(qParser.parse(QueryParserBase.escape(term)), Occur.SHOULD);
            this.query.add(bc);
        }
        this.query.setMinimumNumberShouldMatch(this.uniqueQueryTerms.size());
        if (LOG.isDebugEnabled()) {
            LOG.debug("TEQ {} uQt={}", this.query, this.uniqueQueryTerms);
        }
    }

    /**
     * Reduce the number of terms that must match by one.
     *
     * @return True, if query was relaxed, false, if no terms left to relax the
     * query
     */
    @Override
    public boolean relax() {
        final int matchCount = this.query.getMinimumNumberShouldMatch();
        if (matchCount > 1) {
            if (LOG.isDebugEnabled()) {
                LOG.debug("Relax to {}/{}", matchCount - 1, this.uniqueQueryTerms.size());
            }
            this.query.setMinimumNumberShouldMatch(matchCount - 1);
            return true;
        }
        return false;
    }

    /**
     * Get the query object. This object is directly changed on each call to
     * {@link #relax()}, so there's no need to re-get it every time after relaxing
     * the query.
     *
     * @return Current query object
     */
    @NotNull
    @Override
    public BooleanQuery getQueryObj() {
        return this.query;
    }

    /**
     * Get the list of terms from the original query. Stop-words are removed.
     *
     * @return List of query terms with stop-words removed
     */
    @NotNull
    @Override
    public Collection<String> getQueryTerms() {
        return Collections.unmodifiableCollection(this.queryTerms);
    }
}