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Posted to issues@lucene.apache.org by GitBox <gi...@apache.org> on 2021/05/07 07:02:57 UTC
[GitHub] [lucene] zacharymorn commented on a change in pull request #101: LUCENE-9335: [Discussion Only] Add BMM scorer and use it for pure disjunction term query
zacharymorn commented on a change in pull request #101:
URL: https://github.com/apache/lucene/pull/101#discussion_r627975325
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File path: lucene/core/src/java/org/apache/lucene/search/BlockMaxMaxscoreScorer.java
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@@ -0,0 +1,339 @@
+/*
+ * 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.
+ */
+package org.apache.lucene.search;
+
+import static org.apache.lucene.search.ScorerUtil.costWithMinShouldMatch;
+
+import java.io.IOException;
+import java.util.*;
+
+/** Scorer implementing Block-Max Maxscore algorithm */
+public class BlockMaxMaxscoreScorer extends Scorer {
+ private final ScoreMode scoreMode;
+ private final int scalingFactor;
+
+ // current doc ID of the leads
+ private int doc;
+
+ // doc id boundary that all scorers maxScore are valid
+ private int upTo = -1;
+
+ // heap of scorers ordered by doc ID
+ private final DisiPriorityQueue essentialsScorers;
+
+ // list of scorers whose sum of maxScore is less than minCompetitiveScore, ordered by maxScore
+ private final List<DisiWrapper> nonEssentialScorers;
+
+ // sum of max scores of scorers in nonEssentialScorers list
+ private long nonEssentialMaxScoreSum;
+
+ // sum of score of scorers in essentialScorers list that are positioned on matching doc
+ private long matchedDocScoreSum;
+
+ private long cost;
+
+ private final MaxScoreSumPropagator maxScoreSumPropagator;
+
+ private final List<Scorer> scorers;
+
+ // scaled min competitive score
+ private long minCompetitiveScore = 0;
+
+ /**
+ * Constructs a Scorer
+ *
+ * @param weight The weight to be used.
+ * @param scorers The sub scorers this Scorer should iterate on for optional clauses
+ * @param scoreMode The scoreMode
+ */
+ public BlockMaxMaxscoreScorer(Weight weight, List<Scorer> scorers, ScoreMode scoreMode)
+ throws IOException {
+ super(weight);
+ assert scoreMode == ScoreMode.TOP_SCORES;
+
+ this.scoreMode = scoreMode;
+ this.doc = -1;
+ this.scorers = scorers;
+ this.cost =
+ costWithMinShouldMatch(
+ scorers.stream().map(Scorer::iterator).mapToLong(DocIdSetIterator::cost),
+ scorers.size(),
+ 1);
+
+ essentialsScorers = new DisiPriorityQueue(scorers.size());
+ nonEssentialScorers = new LinkedList<>();
+
+ scalingFactor = WANDScorer.getScalingFactor(scorers);
+ maxScoreSumPropagator = new MaxScoreSumPropagator(scorers);
+
+ for (Scorer scorer : scorers) {
+ nonEssentialScorers.add(new DisiWrapper(scorer));
+ }
+ }
+
+ @Override
+ public DocIdSetIterator iterator() {
+ return TwoPhaseIterator.asDocIdSetIterator(twoPhaseIterator());
+ }
+
+ @Override
+ public TwoPhaseIterator twoPhaseIterator() {
+ DocIdSetIterator approximation =
+ new DocIdSetIterator() {
+ private long lastMinCompetitiveScore;
+
+ @Override
+ public int docID() {
+ return doc;
+ }
+
+ @Override
+ public int nextDoc() throws IOException {
+ return advance(doc + 1);
+ }
+
+ @Override
+ public int advance(int target) throws IOException {
+ doAdvance(target);
+
+ while (doc != DocIdSetIterator.NO_MORE_DOCS
+ && nonEssentialMaxScoreSum + matchedDocScoreSum < minCompetitiveScore) {
+ doAdvance(doc + 1);
+ }
+
+ return doc;
+ }
+
+ private void doAdvance(int target) throws IOException {
+ matchedDocScoreSum = 0;
+ // Find next smallest doc id that is larger than or equal to target from the essential
+ // scorers
+
+ // If the next candidate doc id is still within interval boundary,
+ if (lastMinCompetitiveScore == minCompetitiveScore && target <= upTo) {
+ while (essentialsScorers.top().doc < target) {
+ DisiWrapper w = essentialsScorers.pop();
+ w.doc = w.iterator.advance(target);
+ essentialsScorers.add(w);
+ }
+
+ if (essentialsScorers.top().doc <= upTo) {
+ doc = essentialsScorers.top().doc;
+
+ if (doc == NO_MORE_DOCS) {
+ return;
+ }
+ } else {
+ doc = upTo + 1;
+ }
+ } else {
+ lastMinCompetitiveScore = minCompetitiveScore;
+ // Next candidate doc id is above interval boundary, or minCompetitive has increased.
+ // Find next interval boundary.
+ // Block boundary alignment strategy is adapted from "Optimizing Top-k Document
+ // Retrieval Strategies for Block-Max Indexes" by Dimopoulos, Nepomnyachiy and Suel.
+ // Find the block interval boundary that is the minimum of all participating scorer's
+ // block boundary. Then run BMM within each interval.
+ updateUpToAndMaxScore(target);
+
+ repartitionLists();
+
+ // maxScore of all scorers sum to less than minCompetitiveScore, no more result is
+ // available up to upTo
+ if (essentialsScorers.size() == 0) {
+ // current bound no long valid
+ doc = upTo + 1;
+ } else {
+ doc = essentialsScorers.top().doc;
+
+ if (doc == NO_MORE_DOCS) {
+ return;
+ }
+ }
+ }
+
+ for (DisiWrapper w : essentialsScorers) {
+ if (w.doc == doc && doc != NO_MORE_DOCS) {
+ matchedDocScoreSum += WANDScorer.scaleMaxScore(w.scorer.score(), scalingFactor);
+ }
+ }
+ }
+
+ private void updateUpToAndMaxScore(int target) throws IOException {
+ while (essentialsScorers.size() > 0) {
+ nonEssentialScorers.add(essentialsScorers.pop());
+ }
+
+ // reset upTo
+ upTo = DocIdSetIterator.NO_MORE_DOCS;
+ for (DisiWrapper w : nonEssentialScorers) {
+ if (w.doc < target) {
+ upTo = Math.min(w.scorer.advanceShallow(target), upTo);
+ } else {
+ upTo = Math.min(w.scorer.advanceShallow(w.doc), upTo);
+ }
+ }
+ assert target <= upTo;
+
+ for (DisiWrapper w : nonEssentialScorers) {
+ if (w.doc <= upTo) {
+ w.maxScore = WANDScorer.scaleMaxScore(w.scorer.getMaxScore(upTo), scalingFactor);
+ } else {
+ // This scorer won't be able to contribute to match for target, setting its maxScore
+ // to 0 so it goes into nonEssentialList
+ w.maxScore = 0;
+ }
+ if (w.doc < target) {
+ w.doc = w.iterator.advance(target);
+ }
Review comment:
Hmm I think the purpose here is similar to https://github.com/jpountz/lucene/blob/ce2e5baed8831aac0f44398b97c54264293beb40/lucene/core/src/java/org/apache/lucene/search/BlockMaxMaxscoreScorer.java#L117-L120, to make sure scorer gets positioned on or after `target` if `upTo` is updated. But your approach would require less positioning than mine since it only updates the ones in essential list.
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