Add getMapper(field) to Mapper, so both field with multifields and ob…

…ject mappers can provide underlying field mappers

server/src/main/java/org/elasticsearch/index/mapper/FieldAliasMapper.java

@@ -69,6 +69,11 @@ public Iterator<Mapper> iterator() {
         return Collections.emptyIterator();
     }
 
+    @Override
+    public Mapper getMapper(String field) {
+        return null;
+    }
+
     @Override
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         return builder.startObject(simpleName()).field("type", CONTENT_TYPE).field(Names.PATH, path).endObject();

server/src/main/java/org/elasticsearch/index/mapper/FieldMapper.java

@@ -306,6 +306,17 @@ public Iterator<Mapper> iterator() {
         return multiFieldsIterator();
     }
 
+    @Override
+    public Mapper getMapper(String field) {
+        while (iterator().hasNext()) {
+            Mapper mapper = iterator().next();
+            if (mapper.simpleName().equals(field)) {
+               return mapper;
+            }
+        }
+        return null;
+    }
+
     protected Iterator<Mapper> multiFieldsIterator() {
         return Iterators.forArray(multiFields.mappers);
     }

server/src/main/java/org/elasticsearch/index/mapper/Mapper.java

@@ -145,4 +145,12 @@ public static FieldType freezeAndDeduplicateFieldType(FieldType fieldType) {
      * Defines how this mapper counts towards {@link MapperService#INDEX_MAPPING_TOTAL_FIELDS_LIMIT_SETTING}.
      */
     public abstract int getTotalFieldsCount();
+
+    /**
+     * Returns a submapper for this mapper, if it exists.
+     *
+     * @param field field name from which to obtain the mapper
+     * @return submapper
+     */
+    public abstract Mapper getMapper(String field);
 }