Fix inner_hits retrieval when stored fields are disabled (#34652)

This is the backport of #33018, a change was needed to handle indices with multiple types.
This change throws an error if stored fields are disabled on `inner_hits` for an index with multiple types

Closes #32941

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

@@ -282,6 +282,16 @@ protected Query doToQuery(QueryShardContext context) throws IOException {
         if (!nestedObjectMapper.nested().isNested()) {
             throw new IllegalStateException("[" + NAME + "] nested object under path [" + path + "] is not of nested type");
         }
+        if (innerHitBuilder != null &&
+            innerHitBuilder.getStoredFieldsContext() != null &&
+            innerHitBuilder.getStoredFieldsContext().fetchFields() == false &&
+                context.getMapperService().types().size() > 1) {
+
+            // for multi types indices we need to retrieve the _uid to extract the type of the document
+            // so it is not allowed to disable stored fields
+            throw new IllegalArgumentException("It is not allowed to disable stored fields [_none_] inside [inner_hits] on an index with" +
+                "multiple types.");
+        }
         final BitSetProducer parentFilter;
         Query innerQuery;
         ObjectMapper objectMapper = context.nestedScope().getObjectMapper();

server/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java

@@ -277,7 +277,16 @@ private SearchHit createNestedSearchHit(SearchContext context,
                 storedToRequestedFields, subReaderContext);
         }
 
-        DocumentMapper documentMapper = context.mapperService().documentMapper(uid.type());
+        final String typeText;
+        if (uid != null && uid.type() != null) {
+            typeText = uid.type();
+        } else {
+            // stored fields are disabled but it is not allowed to disable them on inner hits
+            // if the index has multiple types so we can assume that the index has a single type.
+            assert context.mapperService().types().size() == 1;
+            typeText = context.mapperService().types().iterator().next();
+        }
+        DocumentMapper documentMapper = context.mapperService().documentMapper(typeText);
         SourceLookup sourceLookup = context.lookup().source();
         sourceLookup.setSegmentAndDocument(subReaderContext, nestedSubDocId);
 

server/src/test/java/org/elasticsearch/search/aggregations/metrics/TopHitsIT.java

@@ -1052,7 +1052,7 @@ public void testNoStoredFields() throws Exception {
             for (SearchHit hit : hits) {
                 assertThat(hit.getSourceAsMap(), nullValue());
                 assertThat(hit.getId(), nullValue());
-                assertThat(hit.getType(), nullValue());
+                assertThat(hit.getType(), equalTo(null));
             }
         }
     }

server/src/test/java/org/elasticsearch/search/source/MetadataFetchingIT.java

@@ -18,17 +18,36 @@
  */
 package org.elasticsearch.search.source;
 
+import org.apache.lucene.search.join.ScoreMode;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.ExceptionsHelper;
+import org.elasticsearch.Version;
 import org.elasticsearch.action.search.SearchPhaseExecutionException;
 import org.elasticsearch.action.search.SearchResponse;
+import org.elasticsearch.cluster.metadata.IndexMetaData;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.index.query.InnerHitBuilder;
+import org.elasticsearch.index.query.NestedQueryBuilder;
+import org.elasticsearch.index.query.TermQueryBuilder;
 import org.elasticsearch.search.SearchContextException;
+import org.elasticsearch.search.SearchHits;
+import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
 import org.elasticsearch.test.ESIntegTestCase;
 
+import java.util.Collections;
+
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
+import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.nullValue;
 
 public class MetadataFetchingIT extends ESIntegTestCase {
+    @Override
+    protected boolean forbidPrivateIndexSettings() {
+        // needed to create an index with multiple types
+        return false;
+    }
+
     public void testSimple() {
         assertAcked(prepareCreate("test"));
         ensureGreen();
@@ -54,6 +73,56 @@ public void testSimple() {
         assertThat(response.getHits().getAt(0).getSourceAsString(), nullValue());
     }
 
+    public void testInnerHits() {
+        assertAcked(prepareCreate("test_with_types")
+            .addMapping("type1", "nested", "type=nested")
+            .addMapping("type2", "nested", "type=nested")
+            .setSettings(Settings.builder().put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT.minimumCompatibilityVersion())));
+        assertAcked(prepareCreate("test").addMapping("_doc", "nested", "type=nested"));
+        ensureGreen();
+        client().prepareIndex("test", "_doc", "1")
+            .setSource("field", "value", "nested", Collections.singletonMap("title", "foo")).execute().actionGet();
+        client().prepareIndex("test_with_types", "type1", "1")
+            .setSource("field", "value", "nested", Collections.singletonMap("title", "foo")).execute().actionGet();
+        refresh();
+
+        SearchResponse response = client()
+            .prepareSearch("test")
+            .storedFields("_none_")
+            .setFetchSource(false)
+            .setQuery(
+                new NestedQueryBuilder("nested", new TermQueryBuilder("nested.title", "foo"), ScoreMode.Total)
+                    .innerHit(new InnerHitBuilder()
+                        .setStoredFieldNames(Collections.singletonList("_none_"))
+                        .setFetchSourceContext(new FetchSourceContext(false)))
+            )
+            .get();
+        assertThat(response.getHits().totalHits, equalTo(1L));
+        assertThat(response.getHits().getAt(0).getId(), nullValue());
+        assertThat(response.getHits().getAt(0).getType(), equalTo(null));
+        assertThat(response.getHits().getAt(0).getSourceAsString(), nullValue());
+        assertThat(response.getHits().getAt(0).getInnerHits().size(), equalTo(1));
+        SearchHits hits = response.getHits().getAt(0).getInnerHits().get("nested");
+        assertThat(hits.totalHits, equalTo(1L));
+        assertThat(hits.getAt(0).getId(), nullValue());
+        assertThat(hits.getAt(0).getType(), equalTo("_doc"));
+        assertThat(hits.getAt(0).getSourceAsString(), nullValue());
+
+        ElasticsearchException exc = expectThrows(ElasticsearchException.class, () -> client()
+            .prepareSearch("test_with_types")
+            .storedFields("_none_")
+            .setFetchSource(false)
+            .setAllowPartialSearchResults(false)
+            .setQuery(
+                new NestedQueryBuilder("nested", new TermQueryBuilder("nested.title", "foo"), ScoreMode.Total)
+                    .innerHit(new InnerHitBuilder()
+                        .setStoredFieldNames(Collections.singletonList("_none_"))
+                        .setFetchSourceContext(new FetchSourceContext(false)))
+            )
+            .get());
+        assertThat(exc.getDetailedMessage(), containsString("It is not allowed to disable stored fields"));
+    }
+
     public void testWithRouting() {
         assertAcked(prepareCreate("test"));
         ensureGreen();