home | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Lucene example source code file (ScorerDocQueue.java)

This example Lucene source code file (ScorerDocQueue.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

heapedscorerdoc, heapedscorerdoc, io, ioexception, ioexception, scorer, scorer, scorerdocqueue, scorerdocqueue, spansqueue

The Lucene ScorerDocQueue.java source code

package org.apache.lucene.util;

/**
 * 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.
 */

/* Derived from org.apache.lucene.util.PriorityQueue of March 2005 */

import java.io.IOException;

import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.search.Scorer;

/** A ScorerDocQueue maintains a partial ordering of its Scorers such that the
  least Scorer can always be found in constant time.  Put()'s and pop()'s
  require log(size) time. The ordering is by Scorer.doc().
 *
 * @lucene.internal
 */
public class ScorerDocQueue {  // later: SpansQueue for spans with doc and term positions
  private final HeapedScorerDoc[] heap;
  private final int maxSize;
  private int size;
  
  private class HeapedScorerDoc {
    Scorer scorer;
    int doc;
    
    HeapedScorerDoc(Scorer s) { this(s, s.docID()); }
    
    HeapedScorerDoc(Scorer scorer, int doc) {
      this.scorer = scorer;
      this.doc = doc;
    }
    
    void adjust() { doc = scorer.docID(); }
  }
  
  private HeapedScorerDoc topHSD; // same as heap[1], only for speed

  /** Create a ScorerDocQueue with a maximum size. */
  public ScorerDocQueue(int maxSize) {
    // assert maxSize >= 0;
    size = 0;
    int heapSize = maxSize + 1;
    heap = new HeapedScorerDoc[heapSize];
    this.maxSize = maxSize;
    topHSD = heap[1]; // initially null
  }

  /**
   * Adds a Scorer to a ScorerDocQueue in log(size) time.
   * If one tries to add more Scorers than maxSize
   * a RuntimeException (ArrayIndexOutOfBound) is thrown.
   */
  public final void put(Scorer scorer) {
    size++;
    heap[size] = new HeapedScorerDoc(scorer);
    upHeap();
  }

  /**
   * Adds a Scorer to the ScorerDocQueue in log(size) time if either
   * the ScorerDocQueue is not full, or not lessThan(scorer, top()).
   * @param scorer
   * @return true if scorer is added, false otherwise.
   */
  public boolean insert(Scorer scorer){
    if (size < maxSize) {
      put(scorer);
      return true;
    } else {
      int docNr = scorer.docID();
      if ((size > 0) && (! (docNr < topHSD.doc))) { // heap[1] is top()
        heap[1] = new HeapedScorerDoc(scorer, docNr);
        downHeap();
        return true;
      } else {
        return false;
      }
    }
   }

  /** Returns the least Scorer of the ScorerDocQueue in constant time.
   * Should not be used when the queue is empty.
   */
  public final Scorer top() {
    // assert size > 0;
    return topHSD.scorer;
  }

  /** Returns document number of the least Scorer of the ScorerDocQueue
   * in constant time.
   * Should not be used when the queue is empty.
   */
  public final int topDoc() {
    // assert size > 0;
    return topHSD.doc;
  }
  
  public final float topScore() throws IOException {
    // assert size > 0;
    return topHSD.scorer.score();
  }

  public final boolean topNextAndAdjustElsePop() throws IOException {
    return checkAdjustElsePop(topHSD.scorer.nextDoc() != DocIdSetIterator.NO_MORE_DOCS);
  }

  public final boolean topSkipToAndAdjustElsePop(int target) throws IOException {
    return checkAdjustElsePop(topHSD.scorer.advance(target) != DocIdSetIterator.NO_MORE_DOCS);
  }
  
  private boolean checkAdjustElsePop(boolean cond) {
    if (cond) { // see also adjustTop
      topHSD.doc = topHSD.scorer.docID();
    } else { // see also popNoResult
      heap[1] = heap[size]; // move last to first
      heap[size] = null;
      size--;
    }
    downHeap();
    return cond;
  }

  /** Removes and returns the least scorer of the ScorerDocQueue in log(size)
   * time.
   * Should not be used when the queue is empty.
   */
  public final Scorer pop() {
    // assert size > 0;
    Scorer result = topHSD.scorer;
    popNoResult();
    return result;
  }
  
  /** Removes the least scorer of the ScorerDocQueue in log(size) time.
   * Should not be used when the queue is empty.
   */
  private final void popNoResult() {
    heap[1] = heap[size]; // move last to first
    heap[size] = null;
    size--;
    downHeap();	// adjust heap
  }

  /** Should be called when the scorer at top changes doc() value.
   * Still log(n) worst case, but it's at least twice as fast to <pre>
   *  { pq.top().change(); pq.adjustTop(); }
   * </pre> instead of 
   *  { o = pq.pop(); o.change(); pq.push(o); }
   * </pre>
   */
  public final void adjustTop() {
    // assert size > 0;
    topHSD.adjust();
    downHeap();
  }

  /** Returns the number of scorers currently stored in the ScorerDocQueue. */
  public final int size() {
    return size;
  }

  /** Removes all entries from the ScorerDocQueue. */
  public final void clear() {
    for (int i = 0; i <= size; i++) {
      heap[i] = null;
    }
    size = 0;
  }

  private final void upHeap() {
    int i = size;
    HeapedScorerDoc node = heap[i];		  // save bottom node
    int j = i >>> 1;
    while ((j > 0) && (node.doc < heap[j].doc)) {
      heap[i] = heap[j];			  // shift parents down
      i = j;
      j = j >>> 1;
    }
    heap[i] = node;				  // install saved node
    topHSD = heap[1];
  }

  private final void downHeap() {
    int i = 1;
    HeapedScorerDoc node = heap[i];	          // save top node
    int j = i << 1;				  // find smaller child
    int k = j + 1;
    if ((k <= size) && (heap[k].doc < heap[j].doc)) {
      j = k;
    }
    while ((j <= size) && (heap[j].doc < node.doc)) {
      heap[i] = heap[j];			  // shift up child
      i = j;
      j = i << 1;
      k = j + 1;
      if (k <= size && (heap[k].doc < heap[j].doc)) {
	j = k;
      }
    }
    heap[i] = node;				  // install saved node
    topHSD = heap[1];
  }
}

Other Lucene examples (source code examples)

Here is a short list of links related to this Lucene ScorerDocQueue.java source code file:



my book on functional programming

 

new blog posts

 

Copyright 1998-2019 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.