1 package org.apache.lucene.search;
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20 import java.io.IOException;
22 import org.apache.lucene.document.Document;
23 import org.apache.lucene.index.CorruptIndexException;
24 import org.apache.lucene.index.Term;
25 import org.apache.lucene.document.FieldSelector;
28 * An abstract base class for search implementations. Implements the main search
32 * Note that you can only access hits from a Searcher as long as it is not yet
33 * closed, otherwise an IOException will be thrown.
35 * @deprecated In 4.0 this abstract class is removed/absorbed
39 public abstract class Searcher implements Searchable {
40 /** Search implementation with arbitrary sorting. Finds
41 * the top <code>n</code> hits for <code>query</code>, applying
42 * <code>filter</code> if non-null, and sorting the hits by the criteria in
45 * <p>NOTE: this does not compute scores by default; use
46 * {@link IndexSearcher#setDefaultFieldSortScoring} to
49 * @throws BooleanQuery.TooManyClauses
51 public TopFieldDocs search(Query query, Filter filter, int n,
52 Sort sort) throws IOException {
53 return search(createNormalizedWeight(query), filter, n, sort);
57 * Search implementation with arbitrary sorting and no filter.
58 * @param query The query to search for
59 * @param n Return only the top n results
60 * @param sort The {@link org.apache.lucene.search.Sort} object
61 * @return The top docs, sorted according to the supplied {@link org.apache.lucene.search.Sort} instance
64 public TopFieldDocs search(Query query, int n,
65 Sort sort) throws IOException {
66 return search(createNormalizedWeight(query), null, n, sort);
69 /** Lower-level search API.
71 * <p>{@link Collector#collect(int)} is called for every matching document.
73 * <p>Applications should only use this if they need <i>all</i> of the
74 * matching documents. The high-level search API ({@link
75 * Searcher#search(Query, int)}) is usually more efficient, as it skips
76 * non-high-scoring hits.
77 * <p>Note: The <code>score</code> passed to this method is a raw score.
78 * In other words, the score will not necessarily be a float whose value is
80 * @throws BooleanQuery.TooManyClauses
82 public void search(Query query, Collector results)
84 search(createNormalizedWeight(query), null, results);
87 /** Lower-level search API.
89 * <p>{@link Collector#collect(int)} is called for every matching
91 * <br>Collector-based access to remote indexes is discouraged.
93 * <p>Applications should only use this if they need <i>all</i> of the
94 * matching documents. The high-level search API ({@link
95 * Searcher#search(Query, Filter, int)}) is usually more efficient, as it skips
96 * non-high-scoring hits.
98 * @param query to match documents
99 * @param filter if non-null, used to permit documents to be collected.
100 * @param results to receive hits
101 * @throws BooleanQuery.TooManyClauses
103 public void search(Query query, Filter filter, Collector results)
105 search(createNormalizedWeight(query), filter, results);
108 /** Finds the top <code>n</code>
109 * hits for <code>query</code>, applying <code>filter</code> if non-null.
111 * @throws BooleanQuery.TooManyClauses
113 public TopDocs search(Query query, Filter filter, int n)
115 return search(createNormalizedWeight(query), filter, n);
118 /** Finds the top <code>n</code>
119 * hits for <code>query</code>.
121 * @throws BooleanQuery.TooManyClauses
123 public TopDocs search(Query query, int n)
125 return search(query, null, n);
128 /** Returns an Explanation that describes how <code>doc</code> scored against
129 * <code>query</code>.
131 * <p>This is intended to be used in developing Similarity implementations,
132 * and, for good performance, should not be displayed with every hit.
133 * Computing an explanation is as expensive as executing the query over the
136 public Explanation explain(Query query, int doc) throws IOException {
137 return explain(createNormalizedWeight(query), doc);
140 /** The Similarity implementation used by this searcher. */
141 private Similarity similarity = Similarity.getDefault();
143 /** Expert: Set the Similarity implementation used by this Searcher.
145 * @see Similarity#setDefault(Similarity)
147 public void setSimilarity(Similarity similarity) {
148 this.similarity = similarity;
151 /** Expert: Return the Similarity implementation used by this Searcher.
153 * <p>This defaults to the current value of {@link Similarity#getDefault()}.
155 public Similarity getSimilarity() {
156 return this.similarity;
160 * Creates a normalized weight for a top-level {@link Query}.
161 * The query is rewritten by this method and {@link Query#createWeight} called,
162 * afterwards the {@link Weight} is normalized. The returned {@code Weight}
163 * can then directly be used to get a {@link Scorer}.
166 public Weight createNormalizedWeight(Query query) throws IOException {
167 query = rewrite(query);
168 Weight weight = query.createWeight(this);
169 float sum = weight.sumOfSquaredWeights();
170 // this is a hack for backwards compatibility:
171 float norm = query.getSimilarity(this).queryNorm(sum);
172 if (Float.isInfinite(norm) || Float.isNaN(norm))
174 weight.normalize(norm);
179 * Expert: Creates a normalized weight for a top-level {@link Query}.
180 * The query is rewritten by this method and {@link Query#createWeight} called,
181 * afterwards the {@link Weight} is normalized. The returned {@code Weight}
182 * can then directly be used to get a {@link Scorer}.
183 * @deprecated never ever use this method in {@link Weight} implementations.
184 * Subclasses of Searcher should use {@link #createNormalizedWeight}, instead.
187 protected final Weight createWeight(Query query) throws IOException {
188 return createNormalizedWeight(query);
192 public int[] docFreqs(Term[] terms) throws IOException {
193 int[] result = new int[terms.length];
194 for (int i = 0; i < terms.length; i++) {
195 result[i] = docFreq(terms[i]);
200 abstract public void search(Weight weight, Filter filter, Collector results) throws IOException;
201 abstract public void close() throws IOException;
202 abstract public int docFreq(Term term) throws IOException;
203 abstract public int maxDoc() throws IOException;
204 abstract public TopDocs search(Weight weight, Filter filter, int n) throws IOException;
205 abstract public Document doc(int i) throws CorruptIndexException, IOException;
206 abstract public Document doc(int docid, FieldSelector fieldSelector) throws CorruptIndexException, IOException;
207 abstract public Query rewrite(Query query) throws IOException;
208 abstract public Explanation explain(Weight weight, int doc) throws IOException;
209 abstract public TopFieldDocs search(Weight weight, Filter filter, int n, Sort sort) throws IOException;
210 /* End patch for GCJ bug #15411. */