Searcher


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  
21  import org.apache.lucene.index.Term;
22  import org.apache.lucene.document.Document;
23  
24  /** An abstract base class for search implementations.
25   * Implements the main search methods.
26   * 
27   * <p>Note that you can only access Hits from a Searcher as long as it is
28   * not yet closed, otherwise an IOException will be thrown. 
29   */
30  public abstract class Searcher implements Searchable {
31  
32    /** Returns the documents matching <code>query</code>. 
33     * @throws BooleanQuery.TooManyClauses
34     */
35    public final Hits search(Query query) throws IOException   {
36      return search(query, (Filter)null);
37    }
38  
39    /** Returns the documents matching <code>query</code> and
40     * <code>filter</code>.
41     * @throws BooleanQuery.TooManyClauses
42     */
43    public Hits search(Query query, Filter filter) throws IOException   {
44      return new Hits(this, query, filter);
45    }
46  
47    /** Returns documents matching <code>query</code> sorted by
48     * <code>sort</code>.
49     * @throws BooleanQuery.TooManyClauses
50     */
51    public Hits search(Query query, Sort sort)
52      throws IOException   {
53      return new Hits(this, query, null, sort);
54    }
55  
56    /** Returns documents matching <code>query</code> and <code>filter</code>,
57     * sorted by <code>sort</code>.
58     * @throws BooleanQuery.TooManyClauses
59     */
60    public Hits search(Query query, Filter filter, Sort sort)
61      throws IOException   {
62      return new Hits(this, query, filter, sort);
63    }
64  
65    /** Expert: Low-level search implementation with arbitrary sorting.  Finds
66     * the top <code>n</code> hits for <code>query</code>, applying
67     * <code>filter</code> if non-null, and sorting the hits by the criteria in
68     * <code>sort</code>.
69     *
70     * <p>Applications should usually call {@link
71     * Searcher#search(Query,Filter,Sort)} instead.
72     * @throws BooleanQuery.TooManyClauses
73     */
74    public TopFieldDocs search(Query query, Filter filter, int n,
75                               Sort sort) throws IOException   {
76      return search(createWeight(query), filter, n, sort);
77    }
78  
79    /** Lower-level search API.
80     *
81     * <p>{@link HitCollector#collect(int,float)} is called for every non-zero
82     * scoring document.
83     *
84     * <p>Applications should only use this if they need <i>all</i> of the
85     * matching documents.  The high-level search API ({@link
86     * Searcher#search(Query)}) is usually more efficient, as it skips
87     * non-high-scoring hits.
88     * <p>Note: The <code>score</code> passed to this method is a raw score.
89     * In other words, the score will not necessarily be a float whose value is
90     * between 0 and 1.
91     * @throws BooleanQuery.TooManyClauses
92     */
93    public void search(Query query, HitCollector results)
94      throws IOException   {
95      search(query, (Filter)null, results);
96    }
97  
98    /** Lower-level search API.
99     *
100    * <p>{@link HitCollector#collect(int,float)} is called for every non-zero
101    * scoring document.
102    * <br>HitCollector-based access to remote indexes is discouraged.
103    *
104    * <p>Applications should only use this if they need <i>all</i> of the
105    * matching documents.  The high-level search API ({@link
106    * Searcher#search(Query)}) is usually more efficient, as it skips
107    * non-high-scoring hits.
108    *
109    * @param query to match documents
110    * @param filter if non-null, a bitset used to eliminate some documents
111    * @param results to receive hits
112    * @throws BooleanQuery.TooManyClauses
113    */
114   public void search(Query query, Filter filter, HitCollector results)
115     throws IOException   {
116     search(createWeight(query), filter, results);
117   }
118 
119   /** Expert: Low-level search implementation.  Finds the top <code>n</code>
120    * hits for <code>query</code>, applying <code>filter</code> if non-null.
121    *
122    * <p>Called by {@link Hits}.
123    *
124    * <p>Applications should usually call {@link Searcher#search(Query)} or
125    * {@link Searcher#search(Query,Filter)} instead.
126    * @throws BooleanQuery.TooManyClauses
127    */
128   public TopDocs search(Query query, Filter filter, int n)
129     throws IOException   {
130     return search(createWeight(query), filter, n);
131   }
132 
133   /** Returns an Explanation that describes how <code>doc</code> scored against
134    * <code>query</code>.
135    *
136    * <p>This is intended to be used in developing Similarity implementations,
137    * and, for good performance, should not be displayed with every hit.
138    * Computing an explanation is as expensive as executing the query over the
139    * entire index.
140    */
141   public Explanation explain(Query query, int doc) throws IOException   {
142     return explain(createWeight(query), doc);
143   }
144 
145   /** The Similarity implementation used by this searcher. */
146   private Similarity similarity = Similarity.getDefault();
147 
148   /** Expert: Set the Similarity implementation used by this Searcher.
149    *
150    * @see Similarity#setDefault(Similarity)
151    */
152   public void setSimilarity(Similarity similarity) {
153     this.similarity = similarity;
154   }
155 
156   /** Expert: Return the Similarity implementation used by this Searcher.
157    *
158    * <p>This defaults to the current value of {@link Similarity#getDefault()}.
159    */
160   public Similarity getSimilarity() {
161     return this.similarity;
162   }
163 
164   /**
165    * creates a weight for <code>query</code>
166    * @return new weight
167    */
168   protected Weight createWeight(Query query) throws IOException   {
169       return query.weight(this);
170   }
171 
172   // inherit javadoc
173   public int[] docFreqs(Term[] terms) throws IOException   {
174     int[] result = new int[terms.length];
175     for (int i = 0; i < terms.length; i++) {
176       result[i] = docFreq(terms[i]);
177     }
178     return result;
179   }
180 
181   /* The following abstract methods were added as a workaround for GCJ bug #15411.
182    * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15411
183    */
184   abstract public void search(Weight weight, Filter filter, HitCollector results) throws IOException  ;
185   abstract public void close() throws IOException  ;
186   abstract public int docFreq(Term term) throws IOException  ;
187   abstract public int maxDoc() throws IOException  ;
188   abstract public TopDocs search(Weight weight, Filter filter, int n) throws IOException  ;
189   abstract public Document doc(int i) throws IOException  ;
190   abstract public Query rewrite(Query query) throws IOException  ;
191   abstract public Explanation explain(Weight weight, int doc) throws IOException  ;
192   abstract public TopFieldDocs search(Weight weight, Filter filter, int n, Sort sort) throws IOException  ;
193   /* End patch for GCJ bug #15411. */
194 }
195
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