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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,
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 * See the License for the specific language governing permissions and
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package org.apache.lucene.search.vectorhighlight;

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 FieldFragList.
/** * A weighted implementation of {@link FieldFragList}. */
public class WeightedFieldFragList extends FieldFragList {
a constructor.
Params:
  • fragCharSize – the length (number of chars) of a fragment
/** * 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<>(); List<SubInfo> realSubInfos = new ArrayList<>(); HashSet<String> distinctTerms = new HashSet<>(); 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 ) ); } }