ConjunctionScorer


1   package org.apache.lucene.search;
2   
3   /**
4    * Copyright 2004 The Apache Software Foundation
5    *
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  import java.io.IOException  ;
20  import java.util.Arrays  ;
21  import java.util.Comparator  ;
22  import java.util.Iterator  ;
23  import java.util.LinkedList  ;
24  
25  /** Scorer for conjunctions, sets of queries, all of which are required. */
26  class ConjunctionScorer extends Scorer {
27    private LinkedList   scorers = new LinkedList  ();
28    private boolean firstTime = true;
29    private boolean more = true;
30    private float coord;
31  
32    public ConjunctionScorer(Similarity similarity) {
33      super(similarity);
34    }
35  
36    final void add(Scorer scorer) {
37      scorers.addLast(scorer);
38    }
39  
40    private Scorer first() { return (Scorer)scorers.getFirst(); }
41    private Scorer last() { return (Scorer)scorers.getLast(); }
42  
43    public int doc() { return first().doc(); }
44  
45    public boolean next() throws IOException   {
46      if (firstTime) {
47        init(true);
48      } else if (more) {
49        more = last().next();                       // trigger further scanning
50      }
51      return doNext();
52    }
53    
54    private boolean doNext() throws IOException   {
55      while (more && first().doc() < last().doc()) { // find doc w/ all clauses
56        more = first().skipTo(last().doc());      // skip first upto last
57        scorers.addLast(scorers.removeFirst());   // move first to last
58      }
59      return more;                                // found a doc with all clauses
60    }
61  
62    public boolean skipTo(int target) throws IOException   {
63      if(firstTime) {
64        init(false);
65      }
66      
67      Iterator   i = scorers.iterator();
68      while (more && i.hasNext()) {
69        more = ((Scorer)i.next()).skipTo(target);
70      }
71      
72      if (more)
73        sortScorers();                              // re-sort scorers
74      
75      return doNext();
76    }
77  
78    public float score() throws IOException   {
79      float score = 0.0f;                           // sum scores
80      Iterator   i = scorers.iterator();
81      while (i.hasNext())
82        score += ((Scorer)i.next()).score();
83      score *= coord;
84      return score;
85    }
86    
87    private void init(boolean initScorers) throws IOException   {
88      //  compute coord factor
89      coord = getSimilarity().coord(scorers.size(), scorers.size());
90     
91      more = scorers.size() > 0;
92  
93      if(initScorers){
94        // move each scorer to its first entry
95        Iterator   i = scorers.iterator();
96        while (more && i.hasNext()) {
97          more = ((Scorer)i.next()).next();
98        }
99        if (more)
100         sortScorers(); // initial sort of list
101     }
102 
103     firstTime = false;
104   }
105 
106   private void sortScorers() {
107     // move scorers to an array
108     Scorer[] array = (Scorer[])scorers.toArray(new Scorer[scorers.size()]);
109     scorers.clear();                              // empty the list
110 
111     // note that this comparator is not consistent with equals!
112     Arrays.sort(array, new Comparator  () {         // sort the array
113         public int compare(Object   o1, Object   o2) {
114           return ((Scorer)o1).doc() - ((Scorer)o2).doc();
115         }
116       });
117     
118     for (int i = 0; i < array.length; i++) {
119       scorers.addLast(array[i]);                  // re-build list, now sorted
120     }
121   }
122 
123   public Explanation explain(int doc) {
124     throw new UnsupportedOperationException  ();
125   }
126 
127 }
128
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