Aggregation: Fix AggregationPath.subPath() to not throw ArrayStoreException

Aggregation.subPath() always threw an ArrayStoreException because we were trying to pass a List into System.arraycopy(). This change fixes that bug and adds a test to prevent regression

core/src/main/java/org/elasticsearch/search/aggregations/support/AggregationPath.java

@@ -186,9 +186,8 @@ public class AggregationPath {
     }
 
     public AggregationPath subPath(int offset, int length) {
-        PathElement[] subTokens = new PathElement[length];
+        List<PathElement> subTokens = new ArrayList<>(pathElements.subList(offset, offset + length));
-        System.arraycopy(pathElements, offset, subTokens, 0, length);
+        return new AggregationPath(subTokens);
-        return new AggregationPath(pathElements);
     }
 
     /**

core/src/test/java/org/elasticsearch/search/aggregations/bucket/StringTermsIT.java

@@ -22,11 +22,13 @@ import com.google.common.base.Strings;
 
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.action.index.IndexRequestBuilder;
+import org.elasticsearch.action.search.SearchPhaseExecutionException;
 import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.index.mapper.internal.FieldNamesFieldMapper;
 import org.elasticsearch.index.mapper.internal.IndexFieldMapper;
 import org.elasticsearch.index.query.QueryBuilders;
 import org.elasticsearch.script.Script;
+import org.elasticsearch.search.aggregations.AggregationExecutionException;
 import org.elasticsearch.search.aggregations.Aggregator.SubAggCollectionMode;
 import org.elasticsearch.search.aggregations.bucket.filter.Filter;
 import org.elasticsearch.search.aggregations.bucket.histogram.Histogram;
@@ -995,6 +997,36 @@ public class StringTermsIT extends AbstractTermsTestCase {
         }
     }
 
+    @Test
+    public void singleValuedField_OrderedByIllegalAgg() throws Exception {
+        boolean asc = true;
+        try {
+            client()
+                .prepareSearch("idx")
+                .setTypes("type")
+                .addAggregation(
+                        terms("terms").executionHint(randomExecutionHint()).field(SINGLE_VALUED_FIELD_NAME)
+                                .collectMode(randomFrom(SubAggCollectionMode.values()))
+                                .order(Terms.Order.aggregation("inner_terms>avg", asc))
+                                .subAggregation(terms("inner_terms").field(MULTI_VALUED_FIELD_NAME).subAggregation(avg("avg").field("i"))))
+                .execute().actionGet();
+            fail("Expected an exception");
+        } catch (SearchPhaseExecutionException e) {
+            ElasticsearchException[] rootCauses = e.guessRootCauses();
+            if (rootCauses.length == 1) {
+                ElasticsearchException rootCause = rootCauses[0];
+                if (rootCause instanceof AggregationExecutionException) {
+                    AggregationExecutionException aggException = (AggregationExecutionException) rootCause;
+                    assertThat(aggException.getMessage(), Matchers.startsWith("Invalid terms aggregation order path"));
+                } else {
+                    throw e;
+                }
+            } else {
+                throw e;
+            }
+        }
+    }
+
     @Test
     public void singleValuedField_OrderedBySingleBucketSubAggregationAsc() throws Exception {
         boolean asc = randomBoolean();