content: package org.apache.lucene.search;
  
  /**
   * 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.io.IOException;
  import java.util.HashSet;
  import java.util.Set;
  
  import org.apache.lucene.index.Term;
  import org.apache.lucene.index.TermDocs;
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.search.Explanation.IDFExplanation;
  import org.apache.lucene.util.ReaderUtil;
  import org.apache.lucene.util.ToStringUtils;
  
  /** A Query that matches documents containing a term.
    This may be combined with other terms with a {@link BooleanQuery}.
    */
  public class TermQuery extends Query {
    private Term term;
  
    private class TermWeight extends Weight {
      private final Similarity similarity;
      private float value;
      private float idf;
      private float queryNorm;
      private float queryWeight;
      private IDFExplanation idfExp;
      private final Set<Integer> hash;
  
      public TermWeight(Searcher searcher)
        throws IOException {
        this.similarity = getSimilarity(searcher);
        if (searcher instanceof IndexSearcher) {
          hash = new HashSet<Integer>();
          IndexReader ir = ((IndexSearcher)searcher).getIndexReader();
          final int dfSum[] = new int[1];
          new ReaderUtil.Gather(ir) {
            @Override
            protected void add(int base, IndexReader r) throws IOException {
              int df = r.docFreq(term);
              dfSum[0] += df;
              if (df > 0) {
                hash.add(r.hashCode());
              }
            }
          }.run();
  
          idfExp = similarity.idfExplain(term, searcher, dfSum[0]);
        } else {
          idfExp = similarity.idfExplain(term, searcher);
          hash = null;
        }
  
        idf = idfExp.getIdf();
      }
  
      @Override
      public String toString() { return "weight(" + TermQuery.this + ")"; }
  
      @Override
      public Query getQuery() { return TermQuery.this; }
  
      @Override
      public float getValue() { return value; }
  
      @Override
      public float sumOfSquaredWeights() {
        queryWeight = idf * getBoost();             // compute query weight
        return queryWeight * queryWeight;           // square it
      }
  
      @Override
      public void normalize(float queryNorm) {
        this.queryNorm = queryNorm;
        queryWeight *= queryNorm;                   // normalize query weight
        value = queryWeight * idf;                  // idf for document
      }
  
      @Override
      public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
        // only use the early exit condition if we have an atomic reader, because Lucene 3.x still supports non-atomic readers here:
        if (hash != null && reader.getSequentialSubReaders() == null && !hash.contains(reader.hashCode())) {
          return null;
        }
        
        TermDocs termDocs = reader.termDocs(term);
  
        if (termDocs == null)
          return null;
  
        return new TermScorer(this, termDocs, similarity, reader.norms(term.field()));
      }
  
      @Override
      public Explanation explain(IndexReader reader, int doc)
        throws IOException {
  
        ComplexExplanation result = new ComplexExplanation();
        result.setDescription("weight("+getQuery()+" in "+doc+"), product of:");
  
        Explanation expl = new Explanation(idf, idfExp.explain());
  
        // explain query weight
        Explanation queryExpl = new Explanation();
        queryExpl.setDescription("queryWeight(" + getQuery() + "), product of:");
  
        Explanation boostExpl = new Explanation(getBoost(), "boost");
        if (getBoost() != 1.0f)
          queryExpl.addDetail(boostExpl);
        queryExpl.addDetail(expl);
  
        Explanation queryNormExpl = new Explanation(queryNorm,"queryNorm");
        queryExpl.addDetail(queryNormExpl);
  
        queryExpl.setValue(boostExpl.getValue() *
                           expl.getValue() *
                           queryNormExpl.getValue());
  
        result.addDetail(queryExpl);
  
        // explain field weight
        String field = term.field();
        ComplexExplanation fieldExpl = new ComplexExplanation();
        fieldExpl.setDescription("fieldWeight("+term+" in "+doc+
                                 "), product of:");
  
        Explanation tfExplanation = new Explanation();
        int tf = 0;
        TermDocs termDocs = reader.termDocs(term);
        if (termDocs != null) {
          try {
            if (termDocs.skipTo(doc) && termDocs.doc() == doc) {
              tf = termDocs.freq();
            }
          } finally {
            termDocs.close();
          }
          tfExplanation.setValue(similarity.tf(tf));
          tfExplanation.setDescription("tf(termFreq("+term+")="+tf+")");
        } else {
          tfExplanation.setValue(0.0f);
          tfExplanation.setDescription("no matching term");
        }
        fieldExpl.addDetail(tfExplanation);
        fieldExpl.addDetail(expl);
  
        Explanation fieldNormExpl = new Explanation();
        byte[] fieldNorms = reader.norms(field);
        float fieldNorm =
          fieldNorms!=null ? similarity.decodeNormValue(fieldNorms[doc]) : 1.0f;
        fieldNormExpl.setValue(fieldNorm);
        fieldNormExpl.setDescription("fieldNorm(field="+field+", doc="+doc+")");
        fieldExpl.addDetail(fieldNormExpl);
        
        fieldExpl.setMatch(Boolean.valueOf(tfExplanation.isMatch()));
        fieldExpl.setValue(tfExplanation.getValue() *
                           expl.getValue() *
                           fieldNormExpl.getValue());
  
        result.addDetail(fieldExpl);
        result.setMatch(fieldExpl.getMatch());
        
        // combine them
        result.setValue(queryExpl.getValue() * fieldExpl.getValue());
  
        if (queryExpl.getValue() == 1.0f)
          return fieldExpl;
  
        return result;
      }
    }
  
    /** Constructs a query for the term <code>t</code>. */
    public TermQuery(Term t) {
      term = t;
    }
  
    /** Returns the term of this query. */
    public Term getTerm() { return term; }
  
    @Override
    public Weight createWeight(Searcher searcher) throws IOException {
      return new TermWeight(searcher);
    }
  
    @Override
    public void extractTerms(Set<Term> terms) {
      terms.add(getTerm());
    }
  
    /** Prints a user-readable version of this query. */
    @Override
    public String toString(String field) {
      StringBuilder buffer = new StringBuilder();
      if (!term.field().equals(field)) {
        buffer.append(term.field());
        buffer.append(":");
      }
      buffer.append(term.text());
      buffer.append(ToStringUtils.boost(getBoost()));
      return buffer.toString();
    }
  
    /** Returns true iff <code>o</code> is equal to this. */
    @Override
    public boolean equals(Object o) {
      if (!(o instanceof TermQuery))
        return false;
      TermQuery other = (TermQuery)o;
      return (this.getBoost() == other.getBoost())
        && this.term.equals(other.term);
    }
  
    /** Returns a hash code value for this object.*/
    @Override
    public int hashCode() {
      return Float.floatToIntBits(getBoost()) ^ term.hashCode();
    }
  
  }
  