[BUG] IndicesQueryCache$CachingWeightWrapper#count should delegate to internal weight

[jainankitk]

Describe the bug
Currently, IndicesQueryCache$CachingWeightWrapper#count does not delegate to internal weight object and keeps returning -1 from the Weight#count implementation. Due to this leaf counting cannot be done even when it is supported by Weight implementations like PointRangeQuery#createWeight

Expected behavior
Instrumenting the code for FiltersAggregator and observing with and without the change:

Without this change:

Original Query : class org.apache.lucene.document.LongPoint$1
Rewritten Query : class org.apache.lucene.search.IndexOrDocValuesQuery
Original Query : class org.apache.lucene.document.LongPoint$1
Rewritten Query : class org.apache.lucene.search.IndexOrDocValuesQuery
Wrapper class type : class org.apache.lucene.search.LRUQueryCache$CachingWrapperWeight
Aggregation count from the filters : 0  value : -1 class type : class org.apache.lucene.document.LongPoint$1 : class org.opensearch.indices.IndicesQueryCache$CachingWeightWrapper
Wrapper class type : class org.apache.lucene.search.LRUQueryCache$CachingWrapperWeight
Aggregation count from the filters : 1  value : -1 class type : class org.apache.lucene.document.LongPoint$1 : class org.opensearch.indices.IndicesQueryCache$CachingWeightWrapper

With the change:

Original Query : class org.apache.lucene.document.LongPoint$1
Rewritten Query : class org.apache.lucene.search.IndexOrDocValuesQuery
Original Query : class org.apache.lucene.document.LongPoint$1
Rewritten Query : class org.apache.lucene.search.IndexOrDocValuesQuery
Wrapper class type : class org.apache.lucene.search.LRUQueryCache$CachingWrapperWeight
PointRangeQuery#count method was invoked
Aggregation count from the filters : 0  value : 4349068 class type : class org.apache.lucene.document.LongPoint$1 : class org.opensearch.indices.IndicesQueryCache$CachingWeightWrapper
Wrapper class type : class org.apache.lucene.search.LRUQueryCache$CachingWrapperWeight
PointRangeQuery#count method was invoked
Aggregation count from the filters : 1  value : 5981766 class type : class org.apache.lucene.document.LongPoint$1 : class org.opensearch.indices.IndicesQueryCache$CachingWeightWrapper

Additional context
Instrumentation Code

diff --git a/server/src/main/java/org/opensearch/search/aggregations/bucket/filter/FiltersAggregator.java b/server/src/main/java/org/opensearch/search/aggregations/bucket/filter/FiltersAggregator.java
index 84e0218d8ea..b54b46a8254 100644
--- a/server/src/main/java/org/opensearch/search/aggregations/bucket/filter/FiltersAggregator.java
+++ b/server/src/main/java/org/opensearch/search/aggregations/bucket/filter/FiltersAggregator.java
@@ -175,6 +175,7 @@ public class FiltersAggregator extends BucketsAggregator {
         Weight[] filters = this.filters.get();
         final Bits[] bits = new Bits[filters.length];
         for (int i = 0; i < filters.length; ++i) {
+            System.out.println("Aggregation count from the filters : " + i + "  value : " + filters[i].count(ctx) + " class type : " + filters[i].getQuery().getClass() + " : " + filters[i].getClass());
             bits[i] = Lucene.asSequentialAccessBits(ctx.reader().maxDoc(), filters[i].scorerSupplier(ctx));
         }
         return new LeafBucketCollectorBase(sub, null) {
diff --git a/server/src/main/java/org/opensearch/search/aggregations/bucket/filter/FiltersAggregatorFactory.java b/server/src/main/java/org/opensearch/search/aggregations/bucket/filter/FiltersAggregatorFactory.java
index 8741213f988..be96c0505b2 100644
--- a/server/src/main/java/org/opensearch/search/aggregations/bucket/filter/FiltersAggregatorFactory.java
+++ b/server/src/main/java/org/opensearch/search/aggregations/bucket/filter/FiltersAggregatorFactory.java
@@ -32,10 +32,7 @@
 
 package org.opensearch.search.aggregations.bucket.filter;
 
-import org.apache.lucene.search.IndexSearcher;
-import org.apache.lucene.search.Query;
-import org.apache.lucene.search.ScoreMode;
-import org.apache.lucene.search.Weight;
+import org.apache.lucene.search.*;
 import org.opensearch.index.query.QueryShardContext;
 import org.opensearch.search.aggregations.AggregationInitializationException;
 import org.opensearch.search.aggregations.Aggregator;
@@ -102,7 +99,9 @@ public class FiltersAggregatorFactory extends AggregatorFactory {
                 IndexSearcher contextSearcher = searchContext.searcher();
                 weights = new Weight[filters.length];
                 for (int i = 0; i < filters.length; ++i) {
-                    this.weights[i] = contextSearcher.createWeight(contextSearcher.rewrite(filters[i]), ScoreMode.COMPLETE_NO_SCORES, 1);
+                    System.out.println("Original Query : " + ((IndexOrDocValuesQuery)filters[i]).getIndexQuery().getClass());
+                    System.out.println("Rewritten Query : " + contextSearcher.rewrite(filters[i]).getClass());
+                    this.weights[i] = contextSearcher.createWeight(((IndexOrDocValuesQuery)filters[i]).getIndexQuery(), ScoreMode.COMPLETE_NO_SCORES, 1);
                 }
             } catch (IOException e) {
                 throw new AggregationInitializationException("Failed to initialse filters for aggregation [" + name() + "]", e);

Code change:

diff --git a/server/src/main/java/org/opensearch/indices/IndicesQueryCache.java b/server/src/main/java/org/opensearch/indices/IndicesQueryCache.java
index 2669da3f417..97718aeca34 100644
--- a/server/src/main/java/org/opensearch/indices/IndicesQueryCache.java
+++ b/server/src/main/java/org/opensearch/indices/IndicesQueryCache.java
@@ -186,6 +186,12 @@ public class IndicesQueryCache implements QueryCache, Closeable {
             return in.bulkScorer(context);
         }
 
+        @Override
+        public int count(LeafReaderContext context) throws IOException {
+            System.out.println("Wrapper class type : " + in.getClass());
+            return in.count(context);
+        }
+
         @Override
         public boolean isCacheable(LeafReaderContext ctx) {
             return in.isCacheable(ctx);

[jainankitk]

Related to #9310