|
|
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.
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:
|
The search page
Other Lucene source code examples at this package level
Click here to learn more about this project
