1 package org.apache.lucene.search;
2
3 /**
4 * Licensed to the Apache Software Foundation (ASF) under one or more
5 * contributor license agreements. See the NOTICE file distributed with
6 * this work for additional information regarding copyright ownership.
7 * The ASF licenses this file to You under the Apache License, Version 2.0
8 * (the "License"); you may not use this file except in compliance with
9 * the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 import java.io.IOException;
21
22 import java.util.HashSet;
23
24 import java.util.Set;
25
26 import org.apache.lucene.index.IndexReader;
27 import org.apache.lucene.index.Term;
28
29 /** The abstract base class for queries.
30 <p>Instantiable subclasses are:
31 <ul>
32 <li> {@link TermQuery}
33 <li> {@link MultiTermQuery}
34 <li> {@link BooleanQuery}
35 <li> {@link WildcardQuery}
36 <li> {@link PhraseQuery}
37 <li> {@link PrefixQuery}
38 <li> {@link MultiPhraseQuery}
39 <li> {@link FuzzyQuery}
40 <li> {@link TermRangeQuery}
41 <li> {@link NumericRangeQuery}
42 <li> {@link org.apache.lucene.search.spans.SpanQuery}
43 </ul>
44 <p>A parser for queries is contained in:
45 <ul>
46 <li>{@link org.apache.lucene.queryParser.QueryParser QueryParser}
47 </ul>
48 */
49 public abstract class Query implements java.io.Serializable, Cloneable {
50 private float boost = 1.0f; // query boost factor
51
52 /** Sets the boost for this query clause to <code>b</code>. Documents
53 * matching this clause will (in addition to the normal weightings) have
54 * their score multiplied by <code>b</code>.
55 */
56 public void setBoost(float b) { boost = b; }
57
58 /** Gets the boost for this clause. Documents matching
59 * this clause will (in addition to the normal weightings) have their score
60 * multiplied by <code>b</code>. The boost is 1.0 by default.
61 */
62 public float getBoost() { return boost; }
63
64 /** Prints a query to a string, with <code>field</code> assumed to be the
65 * default field and omitted.
66 * <p>The representation used is one that is supposed to be readable
67 * by {@link org.apache.lucene.queryParser.QueryParser QueryParser}. However,
68 * there are the following limitations:
69 * <ul>
70 * <li>If the query was created by the parser, the printed
71 * representation may not be exactly what was parsed. For example,
72 * characters that need to be escaped will be represented without
73 * the required backslash.</li>
74 * <li>Some of the more complicated queries (e.g. span queries)
75 * don't have a representation that can be parsed by QueryParser.</li>
76 * </ul>
77 */
78 public abstract String toString(String field);
79
80 /** Prints a query to a string. */
81 @Override
82 public String toString() {
83 return toString("");
84 }
85
86 /**
87 * Expert: Constructs an appropriate Weight implementation for this query.
88 *
89 * <p>
90 * Only implemented by primitive queries, which re-write to themselves.
91 */
92 public Weight createWeight(Searcher searcher) throws IOException {
93 throw new UnsupportedOperationException();
94 }
95
96 /**
97 * Expert: Constructs and initializes a Weight for a top-level query.
98 */
99 public Weight weight(Searcher searcher) throws IOException {
100 Query query = searcher.rewrite(this);
101 Weight weight = query.createWeight(searcher);
102 float sum = weight.sumOfSquaredWeights();
103 float norm = getSimilarity(searcher).queryNorm(sum);
104 if (Float.isInfinite(norm) || Float.isNaN(norm))
105 norm = 1.0f;
106 weight.normalize(norm);
107 return weight;
108 }
109
110
111 /** Expert: called to re-write queries into primitive queries. For example,
112 * a PrefixQuery will be rewritten into a BooleanQuery that consists
113 * of TermQuerys.
114 */
115 public Query rewrite(IndexReader reader) throws IOException {
116 return this;
117 }
118
119
120 /** Expert: called when re-writing queries under MultiSearcher.
121 *
122 * Create a single query suitable for use by all subsearchers (in 1-1
123 * correspondence with queries). This is an optimization of the OR of
124 * all queries. We handle the common optimization cases of equal
125 * queries and overlapping clauses of boolean OR queries (as generated
126 * by MultiTermQuery.rewrite()).
127 * Be careful overriding this method as queries[0] determines which
128 * method will be called and is not necessarily of the same type as
129 * the other queries.
130 */
131 public Query combine(Query[] queries) {
132 HashSet<Query> uniques = new HashSet<Query>();
133 for (int i = 0; i < queries.length; i++) {
134 Query query = queries[i];
135 BooleanClause[] clauses = null;
136 // check if we can split the query into clauses
137 boolean splittable = (query instanceof BooleanQuery);
138 if(splittable){
139 BooleanQuery bq = (BooleanQuery) query;
140 splittable = bq.isCoordDisabled();
141 clauses = bq.getClauses();
142 for (int j = 0; splittable && j < clauses.length; j++) {
143 splittable = (clauses[j].getOccur() == BooleanClause.Occur.SHOULD);
144 }
145 }
146 if(splittable){
147 for (int j = 0; j < clauses.length; j++) {
148 uniques.add(clauses[j].getQuery());
149 }
150 } else {
151 uniques.add(query);
152 }
153 }
154 // optimization: if we have just one query, just return it
155 if(uniques.size() == 1){
156 return uniques.iterator().next();
157 }
158 BooleanQuery result = new BooleanQuery(true);
159 for (final Query query : uniques)
160 result.add(query, BooleanClause.Occur.SHOULD);
161 return result;
162 }
163
164
165 /**
166 * Expert: adds all terms occurring in this query to the terms set. Only
167 * works if this query is in its {@link #rewrite rewritten} form.
168 *
169 * @throws UnsupportedOperationException if this query is not yet rewritten
170 */
171 public void extractTerms(Set<Term> terms) {
172 // needs to be implemented by query subclasses
173 throw new UnsupportedOperationException();
174 }
175
176
177
178 /** Expert: merges the clauses of a set of BooleanQuery's into a single
179 * BooleanQuery.
180 *
181 *<p>A utility for use by {@link #combine(Query[])} implementations.
182 */
183 public static Query mergeBooleanQueries(BooleanQuery... queries) {
184 HashSet<BooleanClause> allClauses = new HashSet<BooleanClause>();
185 for (BooleanQuery booleanQuery : queries) {
186 for (BooleanClause clause : booleanQuery) {
187 allClauses.add(clause);
188 }
189 }
190
191 boolean coordDisabled =
192 queries.length==0? false : queries[0].isCoordDisabled();
193 BooleanQuery result = new BooleanQuery(coordDisabled);
194 for(BooleanClause clause2 : allClauses) {
195 result.add(clause2);
196 }
197 return result;
198 }
199
200
201 /** Expert: Returns the Similarity implementation to be used for this query.
202 * Subclasses may override this method to specify their own Similarity
203 * implementation, perhaps one that delegates through that of the Searcher.
204 * By default the Searcher's Similarity implementation is returned.*/
205 public Similarity getSimilarity(Searcher searcher) {
206 return searcher.getSimilarity();
207 }
208
209 /** Returns a clone of this query. */
210 @Override
211 public Object clone() {
212 try {
213 return super.clone();
214 } catch (CloneNotSupportedException e) {
215 throw new RuntimeException("Clone not supported: " + e.getMessage());
216 }
217 }
218
219 @Override
220 public int hashCode() {
221 final int prime = 31;
222 int result = 1;
223 result = prime * result + Float.floatToIntBits(boost);
224 return result;
225 }
226
227 @Override
228 public boolean equals(Object obj) {
229 if (this == obj)
230 return true;
231 if (obj == null)
232 return false;
233 if (getClass() != obj.getClass())
234 return false;
235 Query other = (Query) obj;
236 if (Float.floatToIntBits(boost) != Float.floatToIntBits(other.boost))
237 return false;
238 return true;
239 }
240 }