package org.apache.lucene.search;/** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements.  See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License.  You may obtain a copy of the License at * *     http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */import java.io.IOException;import java.util.HashSet;import java.util.Iterator;import java.util.Set;import org.apache.lucene.index.IndexReader;/** The abstract base class for queries.    <p>Instantiable subclasses are:    <ul>    <li> {@link TermQuery}    <li> {@link MultiTermQuery}    <li> {@link BooleanQuery}    <li> {@link WildcardQuery}    <li> {@link PhraseQuery}    <li> {@link PrefixQuery}    <li> {@link MultiPhraseQuery}    <li> {@link FuzzyQuery}    <li> {@link RangeQuery}    <li> {@link org.apache.lucene.search.spans.SpanQuery}    </ul>    <p>A parser for queries is contained in:    <ul>    <li>{@link org.apache.lucene.queryParser.QueryParser QueryParser}    </ul>*/public abstract class Query implements java.io.Serializable, Cloneable {  private float boost = 1.0f;                     // query boost factor  /** Sets the boost for this query clause to <code>b</code>.  Documents   * matching this clause will (in addition to the normal weightings) have   * their score multiplied by <code>b</code>.   */  public void setBoost(float b) { boost = b; }  /** Gets the boost for this clause.  Documents matching   * this clause will (in addition to the normal weightings) have their score   * multiplied by <code>b</code>.   The boost is 1.0 by default.   */  public float getBoost() { return boost; }  /** Prints a query to a string, with <code>field</code> assumed to be the    * default field and omitted.   * <p>The representation used is one that is supposed to be readable   * by {@link org.apache.lucene.queryParser.QueryParser QueryParser}. However,   * there are the following limitations:   * <ul>   *  <li>If the query was created by the parser, the printed   *  representation may not be exactly what was parsed. For example,   *  characters that need to be escaped will be represented without   *  the required backslash.</li>   * <li>Some of the more complicated queries (e.g. span queries)   *  don't have a representation that can be parsed by QueryParser.</li>   * </ul>   */  public abstract String toString(String field);  /** Prints a query to a string. */  public String toString() {    return toString("");  }  /** Expert: Constructs an appropriate Weight implementation for this query.   *   * <p>Only implemented by primitive queries, which re-write to themselves.   */  protected Weight createWeight(Searcher searcher) throws IOException {    throw new UnsupportedOperationException();  }  /** Expert: Constructs and initializes a Weight for a top-level query. */  public Weight weight(Searcher searcher)    throws IOException {    Query query = searcher.rewrite(this);    Weight weight = query.createWeight(searcher);    float sum = weight.sumOfSquaredWeights();    float norm = getSimilarity(searcher).queryNorm(sum);    weight.normalize(norm);    return weight;  }  /** Expert: called to re-write queries into primitive queries. For example,   * a PrefixQuery will be rewritten into a BooleanQuery that consists   * of TermQuerys.   */  public Query rewrite(IndexReader reader) throws IOException {    return this;  }  /** Expert: called when re-writing queries under MultiSearcher.   *   * Create a single query suitable for use by all subsearchers (in 1-1   * correspondence with queries). This is an optimization of the OR of   * all queries. We handle the common optimization cases of equal   * queries and overlapping clauses of boolean OR queries (as generated   * by MultiTermQuery.rewrite() and RangeQuery.rewrite()).   * Be careful overriding this method as queries[0] determines which   * method will be called and is not necessarily of the same type as   * the other queries.  */  public Query combine(Query[] queries) {    HashSet uniques = new HashSet();    for (int i = 0; i < queries.length; i++) {      Query query = queries[i];      BooleanClause[] clauses = null;      // check if we can split the query into clauses      boolean splittable = (query instanceof BooleanQuery);      if(splittable){        BooleanQuery bq = (BooleanQuery) query;        splittable = bq.isCoordDisabled();        clauses = bq.getClauses();        for (int j = 0; splittable && j < clauses.length; j++) {          splittable = (clauses[j].getOccur() == BooleanClause.Occur.SHOULD);        }      }      if(splittable){        for (int j = 0; j < clauses.length; j++) {          uniques.add(clauses[j].getQuery());        }      } else {        uniques.add(query);      }    }    // optimization: if we have just one query, just return it    if(uniques.size() == 1){        return (Query)uniques.iterator().next();    }    Iterator it = uniques.iterator();    BooleanQuery result = new BooleanQuery(true);    while (it.hasNext())      result.add((Query) it.next(), BooleanClause.Occur.SHOULD);    return result;  }  /**   * Expert: adds all terms occuring in this query to the terms set. Only   * works if this query is in its {@link #rewrite rewritten} form.   *    * @throws UnsupportedOperationException if this query is not yet rewritten   */  public void extractTerms(Set terms) {    // needs to be implemented by query subclasses    throw new UnsupportedOperationException();  }  /** Expert: merges the clauses of a set of BooleanQuery's into a single   * BooleanQuery.   *   *<p>A utility for use by {@link #combine(Query[])} implementations.   */  public static Query mergeBooleanQueries(Query[] queries) {    HashSet allClauses = new HashSet();    for (int i = 0; i < queries.length; i++) {      BooleanClause[] clauses = ((BooleanQuery)queries[i]).getClauses();      for (int j = 0; j < clauses.length; j++) {        allClauses.add(clauses[j]);      }    }    boolean coordDisabled =      queries.length==0? false : ((BooleanQuery)queries[0]).isCoordDisabled();    BooleanQuery result = new BooleanQuery(coordDisabled);    Iterator i = allClauses.iterator();    while (i.hasNext()) {      result.add((BooleanClause)i.next());    }    return result;  }  /** Expert: Returns the Similarity implementation to be used for this query.   * Subclasses may override this method to specify their own Similarity   * implementation, perhaps one that delegates through that of the Searcher.   * By default the Searcher's Similarity implementation is returned.*/  public Similarity getSimilarity(Searcher searcher) {    return searcher.getSimilarity();  }  /** Returns a clone of this query. */  public Object clone() {    try {      return (Query)super.clone();    } catch (CloneNotSupportedException e) {      throw new RuntimeException("Clone not supported: " + e.getMessage());    }  }}