alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

What this is

This file is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Other links

The source code

package org.apache.lucene.search;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed 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.
 */

import java.io.IOException;
import java.util.WeakHashMap;
import java.util.BitSet;
import org.apache.lucene.index.IndexReader;

/** Constrains search results to only match those which also match a provided
 * query.  Results are cached, so that searches after the first on the same
 * index using this filter are much faster.
 *
 * 

This could be used, for example, with a {@link RangeQuery} on a suitably * formatted date field to implement date filtering. One could re-use a single * QueryFilter that matches, e.g., only documents modified within the last * week. The QueryFilter and RangeQuery would only need to be reconstructed * once per day. * * @version $Id: QueryFilter.java,v 1.6 2004/05/08 19:54:12 ehatcher Exp $ */ public class QueryFilter extends Filter { private Query query; private transient WeakHashMap cache = null; /** Constructs a filter which only matches documents matching * query. */ public QueryFilter(Query query) { this.query = query; } public BitSet bits(IndexReader reader) throws IOException { if (cache == null) { cache = new WeakHashMap(); } synchronized (cache) { // check cache BitSet cached = (BitSet) cache.get(reader); if (cached != null) { return cached; } } final BitSet bits = new BitSet(reader.maxDoc()); new IndexSearcher(reader).search(query, new HitCollector() { public final void collect(int doc, float score) { bits.set(doc); // set bit for hit } }); synchronized (cache) { // update cache cache.put(reader, bits); } return bits; } public String toString() { return "QueryFilter("+query+")"; } }

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.