TermQuery.cs

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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,
 * 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.
 */

using System;

using IndexReader = Lucene.Net.Index.IndexReader;
using Term = Lucene.Net.Index.Term;
using TermDocs = Lucene.Net.Index.TermDocs;
using ToStringUtils = Lucene.Net.Util.ToStringUtils;
using IDFExplanation = Lucene.Net.Search.Explanation.IDFExplanation;

namespace Lucene.Net.Search
{
    
    /// <summary>A Query that matches documents containing a term.
    /// This may be combined with other terms with a <see cref="BooleanQuery" />.
    /// </summary>
    [Serializable]
    public class TermQuery:Query
    {
        private Term term;
        
        [Serializable]
        private class TermWeight:Weight
        {
            private void  InitBlock(TermQuery enclosingInstance)
            {
                this.enclosingInstance = enclosingInstance;
            }
            private TermQuery enclosingInstance;
            public TermQuery Enclosing_Instance
            {
                get
                {
                    return enclosingInstance;
                }
                
            }
            private Similarity similarity;
            private float value_Renamed;
            private float idf;
            private float queryNorm;
            private float queryWeight;
            private IDFExplanation idfExp;
            
            public TermWeight(TermQuery enclosingInstance, Searcher searcher)
            {
                InitBlock(enclosingInstance);
                this.similarity = Enclosing_Instance.GetSimilarity(searcher);
                idfExp = similarity.IdfExplain(Enclosing_Instance.term, searcher);
                idf = idfExp.Idf;
            }
            
            public override System.String ToString()
            {
                return "weight(" + Enclosing_Instance + ")";
            }

            public override Query Query
            {
                get { return Enclosing_Instance; }
            }

            public override float Value
            {
                get { return value_Renamed; }
            }

            public override float GetSumOfSquaredWeights()
            {
                queryWeight = idf*Enclosing_Instance.Boost; // compute query weight
                return queryWeight*queryWeight; // square it
            }

            public override void  Normalize(float queryNorm)
            {
                this.queryNorm = queryNorm;
                queryWeight *= queryNorm; // normalize query weight
                value_Renamed = queryWeight * idf; // idf for document
            }
            
            public override Scorer Scorer(IndexReader reader, bool scoreDocsInOrder, bool topScorer)
            {
                TermDocs termDocs = reader.TermDocs(Enclosing_Instance.term);
                
                if (termDocs == null)
                    return null;
                
                return new TermScorer(this, termDocs, similarity, reader.Norms(Enclosing_Instance.term.Field));
            }
            
            public override Explanation Explain(IndexReader reader, int doc)
            {
                
                ComplexExplanation result = new ComplexExplanation();
                result.Description = "weight(" + Query + " in " + doc + "), product of:";
                
                Explanation expl = new Explanation(idf, idfExp.Explain());
                
                // explain query weight
                Explanation queryExpl = new Explanation();
                queryExpl.Description = "queryWeight(" + Query + "), product of:";
                
                Explanation boostExpl = new Explanation(Enclosing_Instance.Boost, "boost");
                if (Enclosing_Instance.Boost != 1.0f)
                    queryExpl.AddDetail(boostExpl);
                queryExpl.AddDetail(expl);
                
                Explanation queryNormExpl = new Explanation(queryNorm, "queryNorm");
                queryExpl.AddDetail(queryNormExpl);
                
                queryExpl.Value = boostExpl.Value * expl.Value * queryNormExpl.Value;
                
                result.AddDetail(queryExpl);
                
                // explain field weight
                System.String field = Enclosing_Instance.term.Field;
                ComplexExplanation fieldExpl = new ComplexExplanation();
                fieldExpl.Description = "fieldWeight(" + Enclosing_Instance.term + " in " + doc + "), product of:";

                Explanation tfExplanation = new Explanation();
                int tf = 0;
                TermDocs termDocs = reader.TermDocs(enclosingInstance.term);
                if (termDocs != null)
                {
                    try
                    {
                        if (termDocs.SkipTo(doc) && termDocs.Doc == doc)
                        {
                            tf = termDocs.Freq;
                        }
                    }
                    finally
                    {
                        termDocs.Close();
                    }
                    tfExplanation.Value = similarity.Tf(tf);
                    tfExplanation.Description = "tf(termFreq(" + enclosingInstance.term + ")=" + tf + ")";
                }
                else
                {
                    tfExplanation.Value = 0.0f;
                    tfExplanation.Description = "no matching term";
                }
                fieldExpl.AddDetail(tfExplanation);
                fieldExpl.AddDetail(expl);
                
                Explanation fieldNormExpl = new Explanation();
                byte[] fieldNorms = reader.Norms(field);
                float fieldNorm = fieldNorms != null?Similarity.DecodeNorm(fieldNorms[doc]):1.0f;
                fieldNormExpl.Value = fieldNorm;
                fieldNormExpl.Description = "fieldNorm(field=" + field + ", doc=" + doc + ")";
                fieldExpl.AddDetail(fieldNormExpl);

                fieldExpl.Match = tfExplanation.IsMatch;
                fieldExpl.Value = tfExplanation.Value * expl.Value * fieldNormExpl.Value;
                
                result.AddDetail(fieldExpl);
                System.Boolean? tempAux = fieldExpl.Match;
                result.Match = tempAux;
                
                // combine them
                result.Value = queryExpl.Value * fieldExpl.Value;
                
                if (queryExpl.Value == 1.0f)
                    return fieldExpl;
                
                return result;
            }
        }
        
        /// <summary>Constructs a query for the term <c>t</c>. </summary>
        public TermQuery(Term t)
        {
            term = t;
        }

        /// <summary>Returns the term of this query. </summary>
        public virtual Term Term
        {
            get { return term; }
        }

        public override Weight CreateWeight(Searcher searcher)
        {
            return new TermWeight(this, searcher);
        }
        
        public override void  ExtractTerms(System.Collections.Generic.ISet<Term> terms)
        {
            terms.Add(Term);
        }
        
        /// <summary>Prints a user-readable version of this query. </summary>
        public override System.String ToString(System.String field)
        {
            System.Text.StringBuilder buffer = new System.Text.StringBuilder();
            if (!term.Field.Equals(field))
            {
                buffer.Append(term.Field);
                buffer.Append(":");
            }
            buffer.Append(term.Text);
            buffer.Append(ToStringUtils.Boost(Boost));
            return buffer.ToString();
        }
        
        /// <summary>Returns true iff <c>o</c> is equal to this. </summary>
        public  override bool Equals(System.Object o)
        {
            if (!(o is TermQuery))
                return false;
            TermQuery other = (TermQuery) o;
            return (this.Boost == other.Boost) && this.term.Equals(other.term);
        }
        
        /// <summary>Returns a hash code value for this object.</summary>
        public override int GetHashCode()
        {
            return BitConverter.ToInt32(BitConverter.GetBytes(Boost), 0) ^ term.GetHashCode();
        }
    }
}