org.apache.solr.search.LuceneQueryOptimizer.java Source code

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Here is the source code for org.apache.solr.search.LuceneQueryOptimizer.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.search;

/* Copyright (c) 2003 The Nutch Organization.  All rights reserved.   */

/* Use subject to the conditions in http://www.nutch.org/LICENSE.txt. */

import org.apache.lucene.search.*;

import java.util.LinkedHashMap;
import java.util.Map;
import java.io.IOException;

/** Utility which converts certain query clauses into {@link QueryWrapperFilter}s and
 * caches these.  Only required {@link TermQuery}s whose boost is zero and
 * whose term occurs in at least a certain fraction of documents are converted
 * to cached filters.  This accelerates query constraints like language,
 * document format, etc., which do not affect ranking but might otherwise slow
 * search considerably. */
// Taken from Nutch and modified - YCS
class LuceneQueryOptimizer {
    private LinkedHashMap cache; // an LRU cache of QueryFilter

    private float threshold;

    /** Construct an optimizer that caches and uses filters for required {@link
     * TermQuery}s whose boost is zero.
     * @param cacheSize the number of QueryFilters to cache
     * @param threshold the fraction of documents which must contain term
     */
    public LuceneQueryOptimizer(final int cacheSize, float threshold) {
        this.cache = new LinkedHashMap(cacheSize, 0.75f, true) {
            @Override
            protected boolean removeEldestEntry(Map.Entry eldest) {
                return size() > cacheSize; // limit size of cache
            }
        };
        this.threshold = threshold;
    }

    public TopDocs optimize(BooleanQuery original, SolrIndexSearcher searcher, int numHits, Query[] queryOut,
            Filter[] filterOut) throws IOException {

        BooleanQuery query = new BooleanQuery();
        BooleanQuery filterQuery = null;

        for (BooleanClause c : original.clauses()) {

            /***
            System.out.println("required="+c.required);
            System.out.println("boost="+c.query.getBoost());
            System.out.println("isTermQuery="+(c.query instanceof TermQuery));
            if (c.query instanceof TermQuery) {
             System.out.println("term="+((TermQuery)c.query).getTerm());
             System.out.println("docFreq="+searcher.docFreq(((TermQuery)c.query).getTerm()));
            }
            ***/
            Query q = c.getQuery();
            if (c.isRequired() // required
                    && q.getBoost() == 0.0f // boost is zero
                    && q instanceof TermQuery // TermQuery
                    && (searcher.docFreq(((TermQuery) q).getTerm()) / (float) searcher.maxDoc()) >= threshold) { // check threshold
                if (filterQuery == null)
                    filterQuery = new BooleanQuery();
                filterQuery.add(q, BooleanClause.Occur.MUST); // filter it
                //System.out.println("WooHoo... qualified to be hoisted to a filter!");
            } else {
                query.add(c); // query it
            }
        }

        Filter filter = null;
        if (filterQuery != null) {
            synchronized (cache) { // check cache
                filter = (Filter) cache.get(filterQuery);
            }
            if (filter == null) { // miss
                filter = new CachingWrapperFilter(new QueryWrapperFilter(filterQuery)); // construct new entry
                synchronized (cache) {
                    cache.put(filterQuery, filter); // cache it
                }
            }
        }

        // YCS: added code to pass out optimized query and filter
        // so they can be used with Hits
        if (queryOut != null && filterOut != null) {
            queryOut[0] = query;
            filterOut[0] = filter;
            return null;
        } else {
            return searcher.search(query, filter, numHits);
        }

    }
}