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    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   }

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