Pass parent filter to inner query in nested query (#10246)

Pass parent filter to inner query so that inner query can utilize the information

Signed-off-by: Heemin Kim <[email protected]>

CHANGELOG.md

@@ -115,6 +115,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Force merge with `only_expunge_deletes` honors max segment size ([#10036](https://github.com/opensearch-project/OpenSearch/pull/10036))
 - Add instrumentation in transport service. ([#10042](https://github.com/opensearch-project/OpenSearch/pull/10042))
 - [Tracing Framework] Add support for SpanKind. ([#10122](https://github.com/opensearch-project/OpenSearch/pull/10122))
+- Pass parent filter to inner query in nested query ([#10246](https://github.com/opensearch-project/OpenSearch/pull/10246))
 
 ### Deprecated
 

server/src/main/java/org/opensearch/index/query/NestedQueryBuilder.java

@@ -318,10 +318,13 @@ protected Query doToQuery(QueryShardContext context) throws IOException {
             parentFilter = context.bitsetFilter(objectMapper.nestedTypeFilter());
         }
 
+        BitSetProducer previousParentFilter = context.getParentFilter();
         try {
+            context.setParentFilter(parentFilter);
             context.nestedScope().nextLevel(nestedObjectMapper);
             innerQuery = this.query.toQuery(context);
         } finally {
+            context.setParentFilter(previousParentFilter);
             context.nestedScope().previousLevel();
         }
 

server/src/main/java/org/opensearch/index/query/QueryShardContext.java

@@ -115,6 +115,7 @@ public class QueryShardContext extends QueryRewriteContext {
     private boolean mapUnmappedFieldAsString;
     private NestedScope nestedScope;
     private final ValuesSourceRegistry valuesSourceRegistry;
+    private BitSetProducer parentFilter;
 
     public QueryShardContext(
         int shardId,
@@ -622,4 +623,12 @@ public BitsetFilterCache getBitsetFilterCache() {
     public AggregationUsageService getUsageService() {
         return valuesSourceRegistry.getUsageService();
     }
+
+    public BitSetProducer getParentFilter() {
+        return parentFilter;
+    }
+
+    public void setParentFilter(BitSetProducer parentFilter) {
+        this.parentFilter = parentFilter;
+    }
 }

server/src/test/java/org/opensearch/index/query/NestedQueryBuilderTests.java

@@ -66,6 +66,8 @@
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.notNullValue;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 public class NestedQueryBuilderTests extends AbstractQueryTestCase<NestedQueryBuilder> {
@@ -411,4 +413,22 @@ public void testDisallowExpensiveQueries() {
         OpenSearchException e = expectThrows(OpenSearchException.class, () -> queryBuilder.toQuery(queryShardContext));
         assertEquals("[joining] queries cannot be executed when 'search.allow_expensive_queries' is set to false.", e.getMessage());
     }
+
+    public void testSetParentFilterInContext() throws Exception {
+        QueryShardContext queryShardContext = createShardContext();
+        QueryBuilder innerQueryBuilder = spy(new MatchAllQueryBuilderTests().createTestQueryBuilder());
+        when(innerQueryBuilder.toQuery(queryShardContext)).thenAnswer(invoke -> {
+            QueryShardContext context = invoke.getArgument(0);
+            if (context.getParentFilter() == null) {
+                throw new Exception("Expect parent filter to be non-null");
+            }
+            return invoke.callRealMethod();
+        });
+        NestedQueryBuilder nqb = new NestedQueryBuilder("nested1", innerQueryBuilder, RandomPicks.randomFrom(random(), ScoreMode.values()));
+
+        assertNull(queryShardContext.getParentFilter());
+        nqb.rewrite(queryShardContext).toQuery(queryShardContext);
+        assertNull(queryShardContext.getParentFilter());
+        verify(innerQueryBuilder).toQuery(queryShardContext);
+    }
 }