msokolov commented on a change in pull request #803: LUCENE-8929: Early
Terminating CollectorManager with Global Hitcount
URL: https://github.com/apache/lucene-solr/pull/803#discussion_r308002900
##########
File path: lucene/core/src/java/org/apache/lucene/search/TopFieldCollector.java
##########
@@ -279,6 +280,125 @@ public void collect(int doc) throws IOException {
}
+ /*
+ * Implements a TopFieldCollector that terminates early based on a global
+ * scoreboard which is shared amongst multiple collectors.
+ * NOTE: This should ideally be outside of TopFieldCollector since it does
+ * not have private access, but we keep it here to limit the visibility
+ * of dependent classes
+ */
+ public static class GlobalStateFieldCollector extends TopFieldCollector {
+
+ final Sort sort;
+ final FieldValueHitQueue<Entry> queue;
+ final AtomicInteger globalTotalHits;
+
+ final GlobalStateCollectorManager.GlobalStateCallback callback;
+
+ public GlobalStateFieldCollector(Sort sort, FieldValueHitQueue<Entry>
queue, int numHits, int totalHitsThreshold,
+ AtomicInteger globalTotalHits,
GlobalStateCollectorManager.GlobalStateCallback callback) {
+ super(queue, numHits, totalHitsThreshold, sort.needsScores());
+ this.sort = sort;
+ this.queue = queue;
+ this.globalTotalHits = globalTotalHits;
+ this.callback = callback;
+ }
+
+ @Override
+ public LeafCollector getLeafCollector(LeafReaderContext context) throws
IOException {
+ docBase = context.docBase;
+
+ final LeafFieldComparator[] comparators = queue.getComparators(context);
+ final int[] reverseMul = queue.getReverseMul();
+ final Sort indexSort = context.reader().getMetaData().getSort();
+ final boolean canEarlyTerminate = canEarlyTerminate(sort, indexSort);
+
+ return new MultiComparatorLeafCollector(comparators, reverseMul) {
+
+ boolean collectedAllCompetitiveHits = false;
+
+ @Override
+ public void setScorer(Scorable scorer) throws IOException {
+ super.setScorer(scorer);
+ updateMinCompetitiveScore(scorer);
+ }
+
+ @Override
+ public void collect(int doc) throws IOException {
+ // Increment local hit counter
+ totalHits++;
+
+ if (queueFull) {
+ if (collectedAllCompetitiveHits || !isHitCompetitive(doc, scorer))
{
+ // since docs are visited in doc Id order, if compare is 0, it
means
+ // this document is largest than anything else in the queue, and
+ // therefore not competitive.
+ if (canEarlyTerminate) {
+ // Check the global scoreboard to see total hits accumulated
yet
+ if (globalTotalHits.incrementAndGet() > totalHitsThreshold) {
+ totalHitsRelation = Relation.GREATER_THAN_OR_EQUAL_TO;
+ throw new CollectionTerminatedException();
+ } else {
+ collectedAllCompetitiveHits = true;
+ }
+ } else if (totalHitsRelation == Relation.EQUAL_TO) {
+ // we just reached totalHitsThreshold, we can start setting
the min
+ // competitive score now
+ //TODO: Should we also update competitive score globally?
+ updateMinCompetitiveScore(scorer);
+ }
+ return;
+ }
+
+ // This hit is competitive - replace bottom element in queue &
adjustTop
+ comparator.copy(bottom.slot, doc);
+ updateBottom(doc);
+ comparator.setBottom(bottom.slot);
+ updateMinCompetitiveScore(scorer);
+ //Increment global hit counter
+ globalTotalHits.incrementAndGet();
+ } else {
+ // Startup transient: queue hasn't gathered numHits yet
+
+ //Increment global hit counter
+ globalTotalHits.incrementAndGet();
+
+ final int slot = totalHits - 1;
+
+ // Copy hit into queue
+ comparator.copy(slot, doc);
+ add(slot, doc);
+ if (queueFull) {
+ comparator.setBottom(bottom.slot);
+ updateMinCompetitiveScore(scorer);
+ }
+ }
+ }
+
+ // Check if hit is competitive and set the global value accordingly
+ private boolean isHitCompetitive(int doc, Scorable scorer) throws
IOException {
+ // Check if hit is locally competitive
+ if (reverseMul * comparator.compareBottom(doc) > 0) {
+ // Hit was competitive locally, but was it globally competitive?
+ if (callback.getGlobalMinCompetitiveScore() > scorer.score()) {
+ return false;
+ } else {
+ // Hit was locally and globally competitive, set the right
+ // global minimum competitive score
+ callback.checkAndUpdateMinCompetitiveScore(scorer.score());
+ return true;
+ }
+ }
+
+ // Hit was not locally competitive hence it cannot
+ // be globally competitive
+ return false;
+ }
Review comment:
There are a lot of different ideas here! I agree that early terminating
after collecting hits, but still counting only needs a shared counter.
The shared/global PQ idea might be worth trying. Of course it's appealing to
have something that works well without having to rely on random document
distribution. I wonder whether thread-contention would give up the gains from
avoiding the extra collection work though. In the case of index-sort, the cost
of collection is usually quite low (just read a docvalue and compare, no
scoring function computation), so eking out gains here is tricky.
I wonder if you could combine this idea with pro-rating to avoid some
contention by collecting into per-segment queues until the pro-rated size is
reached, then posting the results collected so far to a shared queue, and
finally collecting into the global queue? Then in the best (most common, when
docs are random) case, you do all the collection with no coordination and
merge-sort as we do today, and afterwards, check one hit in each segment, find
it's not (globally) competitive, and exit.
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