/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2010, Red Hat, Inc. and/or its affiliates or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat, Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* 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 Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.search.filter.impl;
import java.io.IOException;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.Filter;
import org.hibernate.search.util.impl.SoftLimitMRUCache;
import org.hibernate.search.util.logging.impl.Log;
import org.hibernate.search.util.logging.impl.LoggerFactory;
/**
* A slightly different version of Lucene's original <code>CachingWrapperFilter</code> which
* uses <code>SoftReferences</code> instead of <code>WeakReferences</code> in order to cache
* the filter <code>BitSet</code>.
*
* @author Hardy Ferentschik
* @see org.apache.lucene.search.CachingWrapperFilter
* @see <a href="http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-174">HSEARCH-174</a>
*/
@SuppressWarnings("serial")
public class CachingWrapperFilter extends Filter {
private static final Log log = LoggerFactory.make();
public static final int DEFAULT_SIZE = 5;
/**
* The cache using soft references in order to store the filter bit sets.
*/
private final SoftLimitMRUCache cache;
private final Filter filter;
/**
* Under memory pressure the JVM will release all Soft references,
* so pushing it too high will invalidate all eventually useful other caches.
*/
private static final int HARD_TO_SOFT_RATIO = 15;
/**
* @param filter Filter to cache results of
*/
public CachingWrapperFilter(Filter filter) {
this( filter, DEFAULT_SIZE );
}
/**
* @param filter Filter to cache results of
* @param size soft reference size (gets multiplied by {@link #HARD_TO_SOFT_RATIO}.
*/
public CachingWrapperFilter(Filter filter, int size) {
this.filter = filter;
final int softRefSize = size * HARD_TO_SOFT_RATIO;
if ( log.isDebugEnabled() ) {
log.debugf( "Initialising SoftLimitMRUCache with hard ref size of %d and a soft ref of %d", size, softRefSize );
}
this.cache = new SoftLimitMRUCache( size, softRefSize );
}
@Override
public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
DocIdSet cached = (DocIdSet) cache.get( reader );
if ( cached != null ) {
return cached;
}
synchronized ( cache ) {
cached = (DocIdSet) cache.get( reader );
if ( cached != null ) {
return cached;
}
final DocIdSet docIdSet = filter.getDocIdSet( reader );
cache.put( reader, docIdSet );
return docIdSet;
}
}
@Override
public String toString() {
return this.getClass().getName() + "(" + filter + ")";
}
@Override
public boolean equals(Object o) {
if ( !( o instanceof CachingWrapperFilter ) ) {
return false;
}
return this.filter.equals( ( (CachingWrapperFilter) o ).filter );
}
@Override
public int hashCode() {
return filter.hashCode() ^ 0x1117BF25;
}
}