Revert "Do NOT allow termvectors on nested fields (#32728)"

This reverts commit fdff8f3db0093fa15cfa161f7dec80b715a48a43.

docs/reference/docs/termvectors.asciidoc

@@ -30,10 +30,6 @@ in similar way to the <<query-dsl-multi-match-query,multi match query>>
 [WARNING]
 Note that the usage of `/_termvector` is deprecated in 2.0, and replaced by `/_termvectors`.
 
-[WARNING]
-Term Vectors API doesn't work on nested fields. `/_termvectors` on a nested
-field and any sub-fields of a nested field returns empty results.
-
 [float]
 === Return values
 

rest-api-spec/src/main/resources/rest-api-spec/test/termvectors/50_nested.yml

@@ -1,49 +0,0 @@
-setup:
-  - do:
-      indices.create:
-        index: testidx
-        body:
-          mappings:
-            _doc:
-              properties:
-                nested1:
-                  type : nested
-                  properties:
-                    nested1-text:
-                      type: text
-                object1:
-                  properties:
-                    object1-text:
-                      type: text
-                    object1-nested1:
-                      type: nested
-                      properties:
-                        object1-nested1-text:
-                          type: text
-  - do:
-      index:
-        index: testidx
-        type:  _doc
-        id:    1
-        body:
-          "nested1" : [{ "nested1-text": "text1" }]
-          "object1" : [{ "object1-text": "text2" }, "object1-nested1" : [{"object1-nested1-text" : "text3"}]]
-
-  - do:
-      indices.refresh: {}
-
----
-"Termvectors on nested fields should return empty results":
-
-  - do:
-      termvectors:
-        index: testidx
-        type:  _doc
-        id: 1
-        fields: ["nested1", "nested1.nested1-text", "object1.object1-nested1", "object1.object1-nested1.object1-nested1-text", "object1.object1-text"]
-
-  - is_false: term_vectors.nested1
-  - is_false: term_vectors.nested1\.nested1-text # escaping as the field name contains dot
-  - is_false: term_vectors.object1\.object1-nested1
-  - is_false: term_vectors.object1\.object1-nested1\.object1-nested1-text
-  - is_true: term_vectors.object1\.object1-text

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

@@ -45,7 +45,6 @@ import org.elasticsearch.index.mapper.DocumentMapperForType;
 import org.elasticsearch.index.mapper.KeywordFieldMapper;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.MapperService;
-import org.elasticsearch.index.mapper.ObjectMapper;
 import org.elasticsearch.index.mapper.ParseContext;
 import org.elasticsearch.index.mapper.ParsedDocument;
 import org.elasticsearch.index.mapper.SourceFieldMapper;
@@ -161,7 +160,7 @@ public class TermVectorsService  {
         request.selectedFields(fieldNames.toArray(Strings.EMPTY_ARRAY));
     }
 
-    private static boolean isValidField(MappedFieldType fieldType, IndexShard indexShard) {
+    private static boolean isValidField(MappedFieldType fieldType) {
         // must be a string
         if (fieldType instanceof StringFieldType == false) {
             return false;
@@ -170,16 +169,6 @@ public class TermVectorsService  {
         if (fieldType.indexOptions() == IndexOptions.NONE) {
             return false;
         }
-        // and must not be under nested field
-        int dotIndex = fieldType.name().indexOf('.');
-        while (dotIndex > -1) {
-            String parentField = fieldType.name().substring(0, dotIndex);
-            ObjectMapper mapper = indexShard.mapperService().getObjectMapper(parentField);
-            if (mapper != null && mapper.nested().isNested()) {
-                return false;
-            }
-            dotIndex = fieldType.name().indexOf('.', dotIndex + 1);
-        }
         return true;
     }
 
@@ -188,7 +177,7 @@ public class TermVectorsService  {
         Set<String> validFields = new HashSet<>();
         for (String field : selectedFields) {
             MappedFieldType fieldType = indexShard.mapperService().fullName(field);
-            if (isValidField(fieldType, indexShard) == false) {
+            if (!isValidField(fieldType)) {
                 continue;
             }
             // already retrieved, only if the analyzer hasn't been overridden at the field
@@ -295,7 +284,7 @@ public class TermVectorsService  {
         Collection<DocumentField> documentFields = new HashSet<>();
         for (IndexableField field : doc.getFields()) {
             MappedFieldType fieldType = indexShard.mapperService().fullName(field.name());
-            if (isValidField(fieldType, indexShard) == false) {
+            if (!isValidField(fieldType)) {
                 continue;
             }
             if (request.selectedFields() != null && !request.selectedFields().contains(field.name())) {