Fix inner hits to work with queries wrapped in an indices query.

Closes #26133

Author: martijnvg

core/src/main/java/org/elasticsearch/index/query/IndicesQueryBuilder.java

@@ -33,6 +33,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 
@@ -232,6 +233,12 @@ protected Query doToQuery(QueryShardContext context) throws IOException {
         return noMatchQuery.toQuery(context);
     }
 
+    @Override
+    protected void extractInnerHitBuilders(Map<String, InnerHitContextBuilder> innerHits) {
+        InnerHitContextBuilder.extractInnerHits(innerQuery, innerHits);
+        InnerHitContextBuilder.extractInnerHits(noMatchQuery, innerHits);
+    }
+
     @Override
     public int doHashCode() {
         return Objects.hash(innerQuery, noMatchQuery, Arrays.hashCode(indices));

core/src/test/java/org/elasticsearch/search/fetch/subphase/InnerHitsIT.java

@@ -38,23 +38,21 @@
 import org.elasticsearch.search.SearchHits;
 import org.elasticsearch.search.fetch.subphase.highlight.HighlightBuilder;
 import org.elasticsearch.search.sort.FieldSortBuilder;
-import org.elasticsearch.search.sort.SortBuilders;
 import org.elasticsearch.search.sort.SortOrder;
 import org.elasticsearch.test.ESIntegTestCase;
 
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
-import java.util.Locale;
 import java.util.Map;
 import java.util.function.Function;
 
 import static org.elasticsearch.action.support.WriteRequest.RefreshPolicy.IMMEDIATE;
 import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
 import static org.elasticsearch.common.xcontent.support.XContentMapValues.extractValue;
 import static org.elasticsearch.index.query.QueryBuilders.boolQuery;
-import static org.elasticsearch.index.query.QueryBuilders.constantScoreQuery;
+import static org.elasticsearch.index.query.QueryBuilders.indicesQuery;
 import static org.elasticsearch.index.query.QueryBuilders.matchAllQuery;
 import static org.elasticsearch.index.query.QueryBuilders.matchQuery;
 import static org.elasticsearch.index.query.QueryBuilders.nestedQuery;
@@ -636,4 +634,27 @@ public void testInnerHitsWithIgnoreUnmapped() throws Exception {
         assertSearchHits(response, "1", "3");
     }
 
+    public void testInnerHitsInsideIndicesQuery() throws Exception {
+        assertAcked(prepareCreate("index1").addMapping("message", "comments", "type=nested"));
+        client().prepareIndex("index1", "message", "1").setSource(jsonBuilder().startObject()
+            .field("message", "quick brown fox")
+            .startArray("comments")
+            .startObject().field("message", "fox eat quick").endObject()
+            .startObject().field("message", "fox ate rabbit x y z").endObject()
+            .startObject().field("message", "rabbit got away").endObject()
+            .endArray()
+            .endObject()).get();
+        refresh();
+
+        SearchResponse response = client().prepareSearch()
+            .setQuery(indicesQuery(nestedQuery("comments", matchQuery("comments.message", "fox"), ScoreMode.None)
+                .innerHit(new InnerHitBuilder()), "index1"))
+            .get();
+        assertNoFailures(response);
+        assertHitCount(response, 1);
+
+        assertThat(response.getHits().getAt(0).getInnerHits().get("comments").getTotalHits(), equalTo(2L));
+        assertThat(response.getHits().getAt(0).getInnerHits().get("comments").getAt(0).getNestedIdentity().getOffset(), equalTo(0));
+        assertThat(response.getHits().getAt(0).getInnerHits().get("comments").getAt(1).getNestedIdentity().getOffset(), equalTo(1));
+    }
 }