fieldsortedhitqueue.java

lucene-2.4.0 是一个全文收索的工具包

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 org.apache.lucene.index.IndexReader;
import org.apache.lucene.util.PriorityQueue;

import java.io.IOException;
import java.text.Collator;
import java.util.Locale;

/**
 * Expert: A hit queue for sorting by hits by terms in more than one field.
 * Uses <code>FieldCache.DEFAULT</code> for maintaining internal term lookup tables.
 *
 * <p>Created: Dec 8, 2003 12:56:03 PM
 *
 * @since   lucene 1.4
 * @version $Id: FieldSortedHitQueue.java 695514 2008-09-15 15:42:11Z otis $
 * @see Searcher#search(Query,Filter,int,Sort)
 * @see FieldCache
 */
public class FieldSortedHitQueue
extends PriorityQueue {

  /**
   * Creates a hit queue sorted by the given list of fields.
   * @param reader  Index to use.
   * @param fields Fieldable names, in priority order (highest priority first).  Cannot be <code>null</code> or empty.
   * @param size  The number of hits to retain.  Must be greater than zero.
   * @throws IOException
   */
  public FieldSortedHitQueue (IndexReader reader, SortField[] fields, int size)
  throws IOException {
    final int n = fields.length;
    comparators = new ScoreDocComparator[n];
    this.fields = new SortField[n];
    for (int i=0; i<n; ++i) {
      String fieldname = fields[i].getField();
      comparators[i] = getCachedComparator (reader, fieldname, fields[i].getType(), fields[i].getLocale(), fields[i].getFactory());
      
      if (comparators[i].sortType() == SortField.STRING) {
    	  this.fields[i] = new SortField (fieldname, fields[i].getLocale(), fields[i].getReverse());
      } else {
    	  this.fields[i] = new SortField (fieldname, comparators[i].sortType(), fields[i].getReverse());
      }
    }
    initialize (size);
  }


  /** Stores a comparator corresponding to each field being sorted by */
  protected ScoreDocComparator[] comparators;

  /** Stores the sort criteria being used. */
  protected SortField[] fields;

  /** Stores the maximum score value encountered, needed for normalizing. */
  protected float maxscore = Float.NEGATIVE_INFINITY;

  /** returns the maximum score encountered by elements inserted via insert()
   */
  public float getMaxScore() {
    return maxscore;
  }

  // Update maxscore.
  private final void updateMaxScore(FieldDoc fdoc) {
    maxscore = Math.max(maxscore, fdoc.score);
  }
  
  // The signature of this method takes a FieldDoc in order to avoid
  // the unneeded cast to retrieve the score.
  // inherit javadoc
  public boolean insert(FieldDoc fdoc) {
    updateMaxScore(fdoc);
    return super.insert(fdoc);
  }

  // This overrides PriorityQueue.insert() so that insert(FieldDoc) that
  // keeps track of the score isn't accidentally bypassed.  
  // inherit javadoc
  public boolean insert(Object fdoc) {
    return insert((FieldDoc)fdoc);
  }

  // This overrides PriorityQueue.insertWithOverflow() so that
  // updateMaxScore(FieldDoc) that keeps track of the score isn't accidentally
  // bypassed.
  public Object insertWithOverflow(Object element) {
    updateMaxScore((FieldDoc) element);
    return super.insertWithOverflow(element);
  }
  
  /**
   * Returns whether <code>a</code> is less relevant than <code>b</code>.
   * @param a ScoreDoc
   * @param b ScoreDoc
   * @return <code>true</code> if document <code>a</code> should be sorted after document <code>b</code>.
   */
  protected boolean lessThan (final Object a, final Object b) {
    final ScoreDoc docA = (ScoreDoc) a;
    final ScoreDoc docB = (ScoreDoc) b;

    // run comparators
    final int n = comparators.length;
    int c = 0;
    for (int i=0; i<n && c==0; ++i) {
      c = (fields[i].reverse) ? comparators[i].compare (docB, docA)
                              : comparators[i].compare (docA, docB);
    }
    // avoid random sort order that could lead to duplicates (bug #31241):
    if (c == 0)
      return docA.doc > docB.doc;
    return c > 0;
  }


  /**
   * Given a FieldDoc object, stores the values used
   * to sort the given document.  These values are not the raw
   * values out of the index, but the internal representation
   * of them.  This is so the given search hit can be collated
   * by a MultiSearcher with other search hits.
   * @param  doc  The FieldDoc to store sort values into.
   * @return  The same FieldDoc passed in.
   * @see Searchable#search(Weight,Filter,int,Sort)
   */
  FieldDoc fillFields (final FieldDoc doc) {
    final int n = comparators.length;
    final Comparable[] fields = new Comparable[n];
    for (int i=0; i<n; ++i)
      fields[i] = comparators[i].sortValue(doc);
    doc.fields = fields;
    //if (maxscore > 1.0f) doc.score /= maxscore;   // normalize scores
    return doc;
  }


  /** Returns the SortFields being used by this hit queue. */
  SortField[] getFields() {
    return fields;
  }
  
  static ScoreDocComparator getCachedComparator (IndexReader reader, String field, int type, Locale locale, SortComparatorSource factory)
  throws IOException {
    if (type == SortField.DOC) return ScoreDocComparator.INDEXORDER;
    if (type == SortField.SCORE) return ScoreDocComparator.RELEVANCE;
    FieldCacheImpl.Entry entry = (factory != null)
      ? new FieldCacheImpl.Entry (field, factory)
      : new FieldCacheImpl.Entry (field, type, locale);
    return (ScoreDocComparator)Comparators.get(reader, entry);
  }

  /** Internal cache of comparators. Similar to FieldCache, only
   *  caches comparators instead of term values. */
  static final FieldCacheImpl.Cache Comparators = new FieldCacheImpl.Cache() {

    protected Object createValue(IndexReader reader, Object entryKey)
        throws IOException {
      FieldCacheImpl.Entry entry = (FieldCacheImpl.Entry) entryKey;
      String fieldname = entry.field;
      int type = entry.type;
      Locale locale = entry.locale;
      SortComparatorSource factory = (SortComparatorSource) entry.custom;
      ScoreDocComparator comparator;
      switch (type) {
        case SortField.AUTO:
          comparator = comparatorAuto (reader, fieldname);
          break;
        case SortField.INT:
          comparator = comparatorInt (reader, fieldname);
          break;
        case SortField.FLOAT:
          comparator = comparatorFloat (reader, fieldname);
          break;
        case SortField.LONG:
          comparator = comparatorLong(reader, fieldname);
          break;
        case SortField.DOUBLE:
          comparator = comparatorDouble(reader, fieldname);
          break;
        case SortField.SHORT:
          comparator = comparatorShort(reader, fieldname);
          break;
        case SortField.BYTE:
          comparator = comparatorByte(reader, fieldname);
          break;
        case SortField.STRING:
          if (locale != null) comparator = comparatorStringLocale (reader, fieldname, locale);
          else comparator = comparatorString (reader, fieldname);
          break;
        case SortField.CUSTOM:
          comparator = factory.newComparator (reader, fieldname);
          break;
        default:
          throw new RuntimeException ("unknown field type: "+type);
      }
      return comparator;
    }
  };

   /**
   * Returns a comparator for sorting hits according to a field containing bytes.
   * @param reader  Index to use.
   * @param fieldname  Fieldable containg integer values.
   * @return  Comparator for sorting hits.
   * @throws IOException If an error occurs reading the index.
   */
  static ScoreDocComparator comparatorByte(final IndexReader reader, final String fieldname)
  throws IOException {
    final String field = fieldname.intern();
    final byte[] fieldOrder = FieldCache.DEFAULT.getBytes(reader, field);
    return new ScoreDocComparator() {

      public final int compare (final ScoreDoc i, final ScoreDoc j) {
        final int fi = fieldOrder[i.doc];
        final int fj = fieldOrder[j.doc];
        if (fi < fj) return -1;
        if (fi > fj) return 1;
        return 0;
      }

      public Comparable sortValue (final ScoreDoc i) {
        return new Byte(fieldOrder[i.doc]);
      }

      public int sortType() {
        return SortField.INT;
      }
    };
  }

  /**
   * Returns a comparator for sorting hits according to a field containing shorts.
   * @param reader  Index to use.
   * @param fieldname  Fieldable containg integer values.