/
QueryTermScorer.cs
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/
QueryTermScorer.cs
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using Lucene.Net.Analysis;
using Lucene.Net.Analysis.TokenAttributes;
using Lucene.Net.Index;
using System;
using System.Collections.Generic;
using JCG = J2N.Collections.Generic;
namespace Lucene.Net.Search.Highlight
{
/*
* 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.
*/
/// <summary>
/// <see cref="IScorer"/> implementation which scores text fragments by the number of
/// unique query terms found. This class uses the <see cref="QueryTermExtractor"/>
/// class to process determine the query terms and their boosts to be used.
/// </summary>
// TODO: provide option to boost score of fragments near beginning of document
// based on fragment.getFragNum()
public class QueryTermScorer : IScorer
{
//private TextFragment currentTextFragment = null; // LUCENENET: Not used
private ISet<string> uniqueTermsInFragment;
private float totalScore = 0;
private readonly float maxTermWeight = 0;
private readonly IDictionary<string, WeightedTerm> termsToFind;
private ICharTermAttribute termAtt;
/// <param name="query">
/// a Lucene query (ideally rewritten using <see cref="Query.Rewrite(IndexReader)"/> before
/// being passed to this class and the searcher)
/// </param>
public QueryTermScorer(Query query)
: this(QueryTermExtractor.GetTerms(query))
{
}
/// <param name="query">
/// a Lucene query (ideally rewritten using <see cref="Query.Rewrite(IndexReader)"/> before
/// being passed to this class and the searcher)
/// </param>
/// <param name="fieldName">the Field name which is used to match Query terms</param>
public QueryTermScorer(Query query, string fieldName)
: this(QueryTermExtractor.GetTerms(query, false, fieldName))
{
}
/// <param name="query">
/// a Lucene query (ideally rewritten using <see cref="Query.Rewrite(IndexReader)"/> before
/// being passed to this class and the searcher)
/// </param>
/// <param name="reader">
/// used to compute IDF which can be used to a) score selected
/// fragments better b) use graded highlights eg set font color
/// intensity
/// </param>
/// <param name="fieldName">
/// the field on which Inverse Document Frequency (IDF)
/// calculations are based
/// </param>
public QueryTermScorer(Query query, IndexReader reader, string fieldName)
: this(QueryTermExtractor.GetIdfWeightedTerms(query, reader, fieldName))
{
}
public QueryTermScorer(WeightedTerm[] weightedTerms)
{
termsToFind = new Dictionary<string, WeightedTerm>();
for (int i = 0; i < weightedTerms.Length; i++)
{
if (!termsToFind.TryGetValue(weightedTerms[i].Term, out WeightedTerm existingTerm)
|| (existingTerm is null)
|| (existingTerm.Weight < weightedTerms[i].Weight))
{
// if a term is defined more than once, always use the highest scoring
// Weight
termsToFind[weightedTerms[i].Term] = weightedTerms[i];
maxTermWeight = Math.Max(maxTermWeight, weightedTerms[i].Weight);
}
}
}
/// <summary>
/// <seealso cref="IScorer.Init(TokenStream)"/>
/// </summary>
public virtual TokenStream Init(TokenStream tokenStream)
{
termAtt = tokenStream.AddAttribute<ICharTermAttribute>();
return null;
}
public virtual void StartFragment(TextFragment newFragment)
{
uniqueTermsInFragment = new JCG.HashSet<string>();
//currentTextFragment = newFragment; // LUCENENET: Not used
totalScore = 0;
}
/// <summary>
/// <seealso cref="IScorer.GetTokenScore()"/>
/// </summary>
public virtual float GetTokenScore()
{
string termText = termAtt.ToString();
if (!termsToFind.TryGetValue(termText, out WeightedTerm queryTerm) || queryTerm is null)
{
// not a query term - return
return 0;
}
// found a query term - is it unique in this doc?
if (!uniqueTermsInFragment.Contains(termText))
{
totalScore += queryTerm.Weight;
uniqueTermsInFragment.Add(termText);
}
return queryTerm.Weight;
}
/// <summary>
/// <seealso cref="IScorer.FragmentScore"/>
/// </summary>
public virtual float FragmentScore => totalScore;
public virtual void AllFragmentsProcessed()
{
// this class has no special operations to perform at end of processing
}
/// <summary>
/// The highest weighted term (useful for passing to <see cref="GradientFormatter"/>
/// to set top end of coloring scale.
/// </summary>
public virtual float MaxTermWeight => maxTermWeight;
}
}