original-brownbear commented on code in PR #13542:
URL: https://github.com/apache/lucene/pull/13542#discussion_r1731119841
##########
lucene/core/src/java/org/apache/lucene/search/TotalHitCountCollectorManager.java:
##########
@@ -28,17 +31,77 @@
*/
public class TotalHitCountCollectorManager
implements CollectorManager<TotalHitCountCollector, Integer> {
+
+ /**
+ * Internal state shared across the different collectors that this collector
manager creates. It
+ * tracks leaves seen as an argument of {@link
Collector#getLeafCollector(LeafReaderContext)}
+ * calls, to ensure correctness: if the first partition of a segment early
terminates, count has
+ * been already retrieved for the entire segment hence subsequent partitions
of the same segment
+ * should also early terminate. If the first partition of a segment computes
hit counts,
+ * subsequent partitions of the same segment should do the same, to prevent
their counts from
+ * being retrieve from {@link LRUQueryCache} (which returns counts for the
entire segment)
+ */
+ private final Map<LeafReaderContext, Boolean> seenContexts = new HashMap<>();
+
@Override
public TotalHitCountCollector newCollector() throws IOException {
- return new TotalHitCountCollector();
+ return new LeafPartitionAwareTotalHitCountCollector(seenContexts);
}
@Override
public Integer reduce(Collection<TotalHitCountCollector> collectors) throws
IOException {
+ // TODO this makes the collector manager instance reusable across multiple
searches. It isn't a
+ // strict requirement
+ // but it is currently supported as collector managers normally don't hold
state, while
+ // collectors do.
+ // This currently works but would not allow to perform incremental
reductions in the future. It
+ // would be easy enough
+ // to expose an additional method to the CollectorManager interface to
explicitly clear state,
+ // which index searcher
+ // calls before starting a new search. That feels like overkill at the
moment because there is
+ // no real usecase for it.
+ // An alternative is to document the requirement to not reuse collector
managers across
+ // searches, that would be a
+ // breaking change. Perhaps not needed for now.
+ seenContexts.clear();
int totalHits = 0;
for (TotalHitCountCollector collector : collectors) {
totalHits += collector.getTotalHits();
}
return totalHits;
}
+
+ private static class LeafPartitionAwareTotalHitCountCollector extends
TotalHitCountCollector {
+ private final Map<LeafReaderContext, Boolean> seenContexts;
+
+ LeafPartitionAwareTotalHitCountCollector(Map<LeafReaderContext, Boolean>
seenContexts) {
+ this.seenContexts = seenContexts;
+ }
+
+ @Override
+ public LeafCollector getLeafCollector(LeafReaderContext context) throws
IOException {
+ // TODO we could synchronize on context instead, but then the set would
need to be made
+ // thread-safe as well, probably overkill?
+ synchronized (seenContexts) {
+ Boolean earlyTerminated = seenContexts.get(context);
+ // first time we see this leaf
+ if (earlyTerminated == null) {
+ try {
+ LeafCollector leafCollector = super.getLeafCollector(context);
+ seenContexts.put(context, false);
+ return leafCollector;
+ } catch (CollectionTerminatedException e) {
+ seenContexts.put(context, true);
+ throw e;
+ }
+ }
+ if (earlyTerminated) {
+ // previous partition of the same leaf early terminated
+ throw new CollectionTerminatedException();
+ }
Review Comment:
I would expect the compiler to do that for us already but agreed, that would
look better :)
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