package org.apache.lucene.search.vectorhighlight;
/**
* 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.
*/
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import org.apache.lucene.search.vectorhighlight.FieldFragList.WeightedFragInfo.SubInfo;
import org.apache.lucene.search.vectorhighlight.FieldPhraseList.WeightedPhraseInfo;
import org.apache.lucene.search.vectorhighlight.FieldTermStack.TermInfo;
/**
* A weighted implementation of {@link FieldFragList}.
*/
public class WeightedFieldFragList extends FieldFragList {
/**
* a constructor.
*
* @param fragCharSize the length (number of chars) of a fragment
*/
public WeightedFieldFragList( int fragCharSize ) {
super( fragCharSize );
}
/* (non-Javadoc)
* @see org.apache.lucene.search.vectorhighlight.FieldFragList#add( int startOffset, int endOffset, List<WeightedPhraseInfo> phraseInfoList )
*/
@Override
public void add( int startOffset, int endOffset, List<WeightedPhraseInfo> phraseInfoList ) {
List<SubInfo> tempSubInfos = new ArrayList<SubInfo>();
List<SubInfo> realSubInfos = new ArrayList<SubInfo>();
HashSet<String> distinctTerms = new HashSet<String>();
int length = 0;
for( WeightedPhraseInfo phraseInfo : phraseInfoList ){
float phraseTotalBoost = 0;
for ( TermInfo ti : phraseInfo.getTermsInfos()) {
if ( distinctTerms.add( ti.getText() ) )
phraseTotalBoost += ti.getWeight() * phraseInfo.getBoost();
length++;
}
tempSubInfos.add( new SubInfo( phraseInfo.getText(), phraseInfo.getTermsOffsets(),
phraseInfo.getSeqnum(), phraseTotalBoost ) );
}
// We want that terms per fragment (length) is included into the weight. Otherwise a one-word-query
// would cause an equal weight for all fragments regardless of how much words they contain.
// To avoid that fragments containing a high number of words possibly "outrank" more relevant fragments
// we "bend" the length with a standard-normalization a little bit.
float norm = length * ( 1 / (float)Math.sqrt( length ) );
float totalBoost = 0;
for ( SubInfo tempSubInfo : tempSubInfos ) {
float subInfoBoost = tempSubInfo.getBoost() * norm;
realSubInfos.add( new SubInfo( tempSubInfo.getText(), tempSubInfo.getTermsOffsets(),
tempSubInfo.getSeqnum(), subInfoBoost ));
totalBoost += subInfoBoost;
}
getFragInfos().add( new WeightedFragInfo( startOffset, endOffset, realSubInfos, totalBoost ) );
}
}