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.util.List;
import java.util.Iterator;
import java.io.IOException;
import org.apache.lucene.util.ScorerDocQueue;
/** A Scorer for OR like queries, counterpart of <code>ConjunctionScorer</code>.
* This Scorer implements {@link Scorer#skipTo(int)} and uses skipTo() on the given Scorers.
* @todo Implement score(HitCollector, int).
*/
class DisjunctionSumScorer extends Scorer {
/** The number of subscorers. */
private final int nrScorers;
/** The subscorers. */
protected final List subScorers;
/** The minimum number of scorers that should match. */
private final int minimumNrMatchers;
/** The scorerDocQueue contains all subscorers ordered by their current doc(),
* with the minimum at the top.
* <br>The scorerDocQueue is initialized the first time next() or skipTo() is called.
* <br>An exhausted scorer is immediately removed from the scorerDocQueue.
* <br>If less than the minimumNrMatchers scorers
* remain in the scorerDocQueue next() and skipTo() return false.
* <p>
* After each to call to next() or skipTo()
* <code>currentSumScore</code> is the total score of the current matching doc,
* <code>nrMatchers</code> is the number of matching scorers,
* and all scorers are after the matching doc, or are exhausted.
*/
private ScorerDocQueue scorerDocQueue = null;
private int queueSize = -1; // used to avoid size() method calls on scorerDocQueue
/** The document number of the current match. */
private int currentDoc = -1;
/** The number of subscorers that provide the current match. */
protected int nrMatchers = -1;
private float currentScore = Float.NaN;
/** Construct a <code>DisjunctionScorer</code>.
* @param subScorers A collection of at least two subscorers.
* @param minimumNrMatchers The positive minimum number of subscorers that should
* match to match this query.
* <br>When <code>minimumNrMatchers</code> is bigger than
* the number of <code>subScorers</code>,
* no matches will be produced.
* <br>When minimumNrMatchers equals the number of subScorers,
* it more efficient to use <code>ConjunctionScorer</code>.
*/
public DisjunctionSumScorer( List subScorers, int minimumNrMatchers) {
super(null);
nrScorers = subScorers.size();
if (minimumNrMatchers <= 0) {
throw new IllegalArgumentException("Minimum nr of matchers must be positive");
}
if (nrScorers <= 1) {
throw new IllegalArgumentException("There must be at least 2 subScorers");
}
this.minimumNrMatchers = minimumNrMatchers;
this.subScorers = subScorers;
}
/** Construct a <code>DisjunctionScorer</code>, using one as the minimum number
* of matching subscorers.
*/
public DisjunctionSumScorer(List subScorers) {
this(subScorers, 1);
}
/** Called the first time next() or skipTo() is called to
* initialize <code>scorerDocQueue</code>.
*/
private void initScorerDocQueue() throws IOException {
Iterator si = subScorers.iterator();
scorerDocQueue = new ScorerDocQueue(nrScorers);
queueSize = 0;
while (si.hasNext()) {
Scorer se = (Scorer) si.next();
if (se.next()) { // doc() method will be used in scorerDocQueue.
if (scorerDocQueue.insert(se)) {
queueSize++;
}
}
}
}
/** Scores and collects all matching documents.
* @param hc The collector to which all matching documents are passed through
* {@link HitCollector#collect(int, float)}.
* <br>When this method is used the {@link #explain(int)} method should not be used.
*/
public void score(HitCollector hc) throws IOException {
while (next()) {
hc.collect(currentDoc, currentScore);
}
}
/** Expert: Collects matching documents in a range. Hook for optimization.
* Note that {@link #next()} must be called once before this method is called
* for the first time.
* @param hc The collector to which all matching documents are passed through
* {@link HitCollector#collect(int, float)}.
* @param max Do not score documents past this.
* @return true if more matching documents may remain.
*/
protected boolean score(HitCollector hc, int max) throws IOException {
while (currentDoc < max) {
hc.collect(currentDoc, currentScore);
if (!next()) {
return false;
}
}
return true;
}
public boolean next() throws IOException {
if (scorerDocQueue == null) {
initScorerDocQueue();
}
return (scorerDocQueue.size() >= minimumNrMatchers)
&& advanceAfterCurrent();
}
/** Advance all subscorers after the current document determined by the
* top of the <code>scorerDocQueue</code>.
* Repeat until at least the minimum number of subscorers match on the same
* document and all subscorers are after that document or are exhausted.
* <br>On entry the <code>scorerDocQueue</code> has at least <code>minimumNrMatchers</code>
* available. At least the scorer with the minimum document number will be advanced.
* @return true iff there is a match.
* <br>In case there is a match, </code>currentDoc</code>, </code>currentSumScore</code>,
* and </code>nrMatchers</code> describe the match.
*
* @todo Investigate whether it is possible to use skipTo() when
* the minimum number of matchers is bigger than one, ie. try and use the
* character of ConjunctionScorer for the minimum number of matchers.
* Also delay calling score() on the sub scorers until the minimum number of
* matchers is reached.
* <br>For this, a Scorer array with minimumNrMatchers elements might
* hold Scorers at currentDoc that are temporarily popped from scorerQueue.
*/
protected boolean advanceAfterCurrent() throws IOException {
do { // repeat until minimum nr of matchers
currentDoc = scorerDocQueue.topDoc();
currentScore = scorerDocQueue.topScore();
nrMatchers = 1;
do { // Until all subscorers are after currentDoc
if (! scorerDocQueue.topNextAndAdjustElsePop()) {
if (--queueSize == 0) {
break; // nothing more to advance, check for last match.
}
}
if (scorerDocQueue.topDoc() != currentDoc) {
break; // All remaining subscorers are after currentDoc.
}
currentScore += scorerDocQueue.topScore();
nrMatchers++;
} while (true);
if (nrMatchers >= minimumNrMatchers) {
return true;
} else if (queueSize < minimumNrMatchers) {
return false;
}
} while (true);
}
/** Returns the score of the current document matching the query.
* Initially invalid, until {@link #next()} is called the first time.
*/
public float score() throws IOException { return currentScore; }
public int doc() { return currentDoc; }
/** Returns the number of subscorers matching the current document.
* Initially invalid, until {@link #next()} is called the first time.
*/
public int nrMatchers() {
return nrMatchers;
}
/** Skips to the first match beyond the current whose document number is
* greater than or equal to a given target.
* <br>When this method is used the {@link #explain(int)} method should not be used.
* <br>The implementation uses the skipTo() method on the subscorers.
* @param target The target document number.
* @return true iff there is such a match.
*/
public boolean skipTo(int target) throws IOException {
if (scorerDocQueue == null) {
initScorerDocQueue();
}
if (queueSize < minimumNrMatchers) {
return false;
}
if (target <= currentDoc) {
return true;
}
do {
if (scorerDocQueue.topDoc() >= target) {
return advanceAfterCurrent();
} else if (! scorerDocQueue.topSkipToAndAdjustElsePop(target)) {
if (--queueSize < minimumNrMatchers) {
return false;
}
}
} while (true);
}
/** @return An explanation for the score of a given document. */
public Explanation explain(int doc) throws IOException {
Explanation res = new Explanation();
Iterator ssi = subScorers.iterator();
float sumScore = 0.0f;
int nrMatches = 0;
while (ssi.hasNext()) {
Explanation es = ((Scorer) ssi.next()).explain(doc);
if (es.getValue() > 0.0f) { // indicates match
sumScore += es.getValue();
nrMatches++;
}
res.addDetail(es);
}
if (nrMatchers >= minimumNrMatchers) {
res.setValue(sumScore);
res.setDescription("sum over at least " + minimumNrMatchers
+ " of " + subScorers.size() + ":");
} else {
res.setValue(0.0f);
res.setDescription(nrMatches + " match(es) but at least "
+ minimumNrMatchers + " of "
+ subScorers.size() + " needed");
}
return res;
}
}
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