[Backport 2.x] Fix slice collectors to leaves association with post filter

server/src/main/java/org/opensearch/common/lucene/search/FilteredCollector.java

@@ -40,6 +40,7 @@
 import org.apache.lucene.search.Weight;
 import org.apache.lucene.util.Bits;
 import org.opensearch.common.lucene.Lucene;
+import org.opensearch.search.profile.query.ProfileWeight;
 
 import java.io.IOException;
 
@@ -64,6 +65,9 @@ public Collector getCollector() {
 
     @Override
     public LeafCollector getLeafCollector(LeafReaderContext context) throws IOException {
+        if (filter instanceof ProfileWeight) {
+            ((ProfileWeight) filter).associateCollectorToLeaves(context, collector);
+        }
         final ScorerSupplier filterScorerSupplier = filter.scorerSupplier(context);
         final LeafCollector in = collector.getLeafCollector(context);
         final Bits bits = Lucene.asSequentialAccessBits(context.reader().maxDoc(), filterScorerSupplier);

server/src/main/java/org/opensearch/search/profile/query/ConcurrentQueryProfileBreakdown.java

@@ -83,7 +83,10 @@
             // creates a new weight and breakdown map for each rewritten query. This new breakdown map captures the timing information for
             // the new rewritten query. The sliceCollectorsToLeaves is empty because this breakdown for rewritten query gets created later
             // in search leaf path which doesn't have collector. Also, this is not needed since this breakdown is per leaf and there is no
-            // concurrency involved. An empty sliceCollectorsToLeaves could also happen in the case of early termination.
+            // concurrency involved.
+            assert contexts.size() == 1 : "Unexpected size: "
+                + contexts.size()
+                + " of leaves breakdown in ConcurrentQueryProfileBreakdown of rewritten query for a leaf.";
             AbstractProfileBreakdown<QueryTimingType> breakdown = contexts.values().iterator().next();
             queryNodeTime = breakdown.toNodeTime() + createWeightTime;
             maxSliceNodeTime = 0L;