Handle nested fields with the termvectors REST API in artificial docs (#92568)

docs/changelog/92568.yaml

@@ -0,0 +1,6 @@
+pr: 92568
+summary: Support nested fields for term vectors API when using artificial documents
+area: Search
+type: enhancement
+issues:
+  - 91902

server/src/main/java/org/elasticsearch/index/termvectors/TermVectorsService.java

@@ -35,6 +35,7 @@ import org.elasticsearch.index.mapper.LuceneDocument;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.MappingLookup;
+import org.elasticsearch.index.mapper.NestedPathFieldMapper;
 import org.elasticsearch.index.mapper.ParsedDocument;
 import org.elasticsearch.index.mapper.SourceFieldMapper;
 import org.elasticsearch.index.mapper.SourceToParse;
@@ -185,6 +186,11 @@ public class TermVectorsService {
         if (fieldType.isIndexed() == false) {
             return false;
         }
+        // and must not be the nested path field
+        if (fieldType.name().equals(NestedPathFieldMapper.NAME)) {
+            return false;
+        }
+
         return true;
     }
 
@@ -291,7 +297,13 @@ public class TermVectorsService {
         MemoryIndex index = new MemoryIndex(withOffsets);
         for (Map.Entry<String, Collection<Object>> entry : values.entrySet()) {
             String field = entry.getKey();
-            Analyzer analyzer = getAnalyzerAtField(indexShard, field, perFieldAnalyzer);
+            final Analyzer analyzer;
+            try {
+                analyzer = getAnalyzerAtField(indexShard, field, perFieldAnalyzer);
+            } catch (IllegalArgumentException e) {
+                // failed to get the analyzer for the given field, it could be a metadata field
+                continue;
+            }
             if (entry.getValue() instanceof List) {
                 for (Object text : entry.getValue()) {
                     index.addField(field, text.toString(), analyzer);
@@ -310,25 +322,26 @@ public class TermVectorsService {
         MappingLookup mappingLookup = indexShard.mapperService().mappingLookup();
         ParsedDocument parsedDocument = documentParser.parseDocument(source, mappingLookup);
         // select the right fields and generate term vectors
-        LuceneDocument doc = parsedDocument.rootDoc();
-        Set<String> seenFields = new HashSet<>();
-        Collection<DocumentField> documentFields = new HashSet<>();
-        for (IndexableField field : doc.getFields()) {
-            MappedFieldType fieldType = indexShard.mapperService().fieldType(field.name());
-            if (isValidField(fieldType) == false) {
-                continue;
-            }
-            if (request.selectedFields() != null && request.selectedFields().contains(field.name()) == false) {
-                continue;
-            }
-            if (seenFields.contains(field.name())) {
-                continue;
-            } else {
-                seenFields.add(field.name());
+        final Set<String> seenFields = new HashSet<>();
+        final Collection<DocumentField> documentFields = new HashSet<>();
+        for (LuceneDocument doc : parsedDocument.docs()) {
+            for (IndexableField field : doc.getFields()) {
+                MappedFieldType fieldType = indexShard.mapperService().fieldType(field.name());
+                if (isValidField(fieldType) == false) {
+                    continue;
+                }
+                if (request.selectedFields() != null && request.selectedFields().contains(field.name()) == false) {
+                    continue;
+                }
+                if (seenFields.contains(field.name())) {
+                    continue;
+                } else {
+                    seenFields.add(field.name());
+                }
+                @SuppressWarnings("unchecked")
+                List<Object> values = (List) getValues(doc.getFields(field.name()));
+                documentFields.add(new DocumentField(field.name(), values));
             }
-            @SuppressWarnings("unchecked")
-            List<Object> values = (List) getValues(doc.getFields(field.name()));
-            documentFields.add(new DocumentField(field.name(), values));
         }
         return generateTermVectors(
             indexShard,

server/src/test/java/org/elasticsearch/index/termvectors/TermVectorsServiceTests.java

@@ -30,6 +30,7 @@ import static java.lang.Math.abs;
 import static java.util.stream.Collectors.toList;
 import static org.elasticsearch.action.support.WriteRequest.RefreshPolicy.IMMEDIATE;
 import static org.elasticsearch.xcontent.XContentFactory.jsonBuilder;
+import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.notNullValue;
 
@@ -147,4 +148,49 @@ public class TermVectorsServiceTests extends ESSingleNodeTestCase {
             assertEquals(max, phraseIterator.docFreq());
         }
     }
+
+    public void testArtificialDocWithNestedFields() throws IOException {
+        final XContentBuilder mapping = jsonBuilder().startObject()
+            .startObject("_doc")
+            .startObject("properties")
+            .startObject("group")
+            .field("type", "text")
+            .endObject()
+            .startObject("user")
+            .field("type", "nested")
+            .startObject("properties")
+            .startObject("first")
+            .field("type", "text")
+            .endObject()
+            .startObject("last")
+            .field("type", "text")
+            .endObject()
+            .endObject()
+            .endObject()
+            .endObject()
+            .endObject()
+            .endObject();
+        final Settings settings = Settings.builder().put("number_of_shards", 1).build();
+        createIndex("test", settings, mapping);
+        ensureGreen();
+
+        final TermVectorsRequest request = new TermVectorsRequest().doc(
+            jsonBuilder().startObject()
+                .field("group", "test")
+                .startArray("user")
+                .startObject()
+                .field("first", "John")
+                .field("last", "Smith")
+                .endObject()
+                .endArray()
+                .endObject()
+        ).termStatistics(true);
+
+        final IndicesService indicesService = getInstanceFromNode(IndicesService.class);
+        final IndexService test = indicesService.indexService(resolveIndex("test"));
+        final IndexShard shard = test.getShardOrNull(0);
+        assertThat(shard, notNullValue());
+        final TermVectorsResponse response = TermVectorsService.getTermVectors(shard, request);
+        assertThat(response.getFields(), containsInAnyOrder("group", "user.first", "user.last"));
+    }
 }