/*
* 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.util.ArrayList;
import java.util.BitSet;
import java.util.List;
import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.util.DocIdBitSet;
import org.apache.lucene.util.OpenBitSet;
/**
* Helper class to apply some common optimizations when
* several Filters are applied.
*
* @author Sanne Grinovero
*/
public class FilterOptimizationHelper {
/**
* Returns a new list of DocIdSet, applying binary AND
* on all DocIdSet implemented by using BitSet or OpenBitSet.
* @param docIdSets
* @return the same list if no changes were done
*/
public static List<DocIdSet> mergeByBitAnds(List<DocIdSet> docIdSets) {
int size = docIdSets.size();
List<OpenBitSet> openBitSets = new ArrayList<OpenBitSet>( size );
List<DocIdBitSet> docIdBitSets = new ArrayList<DocIdBitSet>( size );
List<DocIdSet> nonMergeAble = new ArrayList<DocIdSet>( size );
for (DocIdSet set : docIdSets) {
if (set instanceof OpenBitSet) {
openBitSets.add( (OpenBitSet) set );
}
else if (set instanceof DocIdBitSet) {
docIdBitSets.add( (DocIdBitSet) set );
}
else {
nonMergeAble.add( set );
}
}
if ( openBitSets.size() <= 1 && docIdBitSets.size() <= 1 ) {
//skip all work as no optimization is possible
return docIdSets;
}
if ( openBitSets.size() > 0 ) {
nonMergeAble.add( mergeByBitAndsForOpenBitSet( openBitSets ) );
}
if ( docIdBitSets.size() > 0 ) {
nonMergeAble.add( mergeByBitAndsForDocIdBitSet( docIdBitSets ) );
}
return nonMergeAble;
}
/**
* Merges all DocIdBitSet in a new DocIdBitSet using
* binary AND operations, which is usually more efficient
* than using an iterator.
* @param docIdBitSets
* @return a new DocIdBitSet, or the first element if only
* one element was found in the list.
*/
private static DocIdBitSet mergeByBitAndsForDocIdBitSet(List<DocIdBitSet> docIdBitSets) {
int listSize = docIdBitSets.size();
if ( listSize == 1 ) {
return docIdBitSets.get( 0 );
}
//we need to copy the first BitSet because BitSet is modified by .logicalOp
BitSet result = (BitSet) docIdBitSets.get( 0 ).getBitSet().clone();
for ( int i=1; i<listSize; i++ ) {
BitSet bitSet = docIdBitSets.get( i ).getBitSet();
result.and( bitSet );
}
return new DocIdBitSet( result );
}
/**
* Merges all OpenBitSet in a new OpenBitSet using
* binary AND operations, which is usually more efficient
* than using an iterator.
* @param openBitSets
* @return a new OpenBitSet, or the first element if only
* one element was found in the list.
*/
private static OpenBitSet mergeByBitAndsForOpenBitSet(List<OpenBitSet> openBitSets) {
int listSize = openBitSets.size();
if ( listSize == 1 ) {
return openBitSets.get( 0 );
}
//we need to copy the first OpenBitSet because BitSet is modified by .logicalOp
OpenBitSet result = (OpenBitSet) openBitSets.get( 0 ).clone();
for ( int i=1; i<listSize; i++ ) {
OpenBitSet openSet = openBitSets.get( i );
result.intersect( openSet );
}
return result;
}
}