Aggregations: Fix regression bug for the support of terms aggregation on the `_parent` field.

src/main/java/org/elasticsearch/search/aggregations/support/ValuesSource.java

@@ -339,7 +339,7 @@ public abstract class ValuesSource {
 
             @Override
             public SortedBinaryDocValues bytesValues() {
-                throw new UnsupportedOperationException();
+                return atomicFieldData.getBytesValues();
             }
 
             @Override

src/test/java/org/elasticsearch/search/aggregations/bucket/ParentIdAggTests.java

@@ -0,0 +1,62 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.elasticsearch.search.aggregations.bucket;
+
+import org.elasticsearch.action.search.SearchResponse;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.search.aggregations.AggregationBuilders;
+import org.elasticsearch.search.aggregations.bucket.terms.Terms;
+import org.elasticsearch.test.ElasticsearchIntegrationTest;
+import org.junit.Test;
+
+import java.io.IOException;
+
+import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
+import static org.elasticsearch.index.query.QueryBuilders.matchAllQuery;
+import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
+import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertSearchResponse;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.instanceOf;
+
+
+public class ParentIdAggTests extends ElasticsearchIntegrationTest {
+
+    @Test
+    public void testParentIdAggregation() throws IOException {
+        XContentBuilder mapping = jsonBuilder().startObject()
+                .startObject("childtype")
+                .startObject("_parent")
+                .field("type", "parenttype")
+                .field("store", true)
+                .endObject()
+                .endObject();
+        assertAcked(prepareCreate("testidx").addMapping("childtype", mapping));
+        client().prepareIndex("testidx", "childtype").setSource(jsonBuilder().startObject().field("num", 1).endObject()).setParent("p1").get();
+        client().prepareIndex("testidx", "childtype").setSource(jsonBuilder().startObject().field("num", 2).endObject()).setParent("p1").get();
+
+        refresh();
+        ensureGreen("testidx");
+        SearchResponse searchResponse = client().prepareSearch("testidx").setTypes("childtype").setQuery(matchAllQuery()).addAggregation(AggregationBuilders.terms("children").field("_parent")).get();
+        assertThat(searchResponse.getHits().getTotalHits(), equalTo(2l));
+        assertSearchResponse(searchResponse);
+        assertThat(searchResponse.getAggregations().getAsMap().get("children"), instanceOf(Terms.class));
+        Terms terms = (Terms) searchResponse.getAggregations().getAsMap().get("children");
+        assertThat(terms.getBuckets().iterator().next().getDocCount(), equalTo(2l));
+    }
+}