From b3274bd770c01c6166bc2ad52e327e879c331c95 Mon Sep 17 00:00:00 2001
From: Adrien Grand <jpountz@gmail.com>
Date: Thu, 22 May 2014 14:44:32 +0200
Subject: [PATCH] Aggregations: Fix ReverseNestedAggregator to compute the
 parent document correctly.

Close #6278
---
 .../bucket/nested/ReverseNestedAggregator.java             | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/elasticsearch/search/aggregations/bucket/nested/ReverseNestedAggregator.java b/src/main/java/org/elasticsearch/search/aggregations/bucket/nested/ReverseNestedAggregator.java
index ac0dad6335a..b08aae29c15 100644
--- a/src/main/java/org/elasticsearch/search/aggregations/bucket/nested/ReverseNestedAggregator.java
+++ b/src/main/java/org/elasticsearch/search/aggregations/bucket/nested/ReverseNestedAggregator.java
@@ -105,7 +105,12 @@ public class ReverseNestedAggregator extends SingleBucketAggregator implements R
         }
 
         // fast forward to retrieve the parentDoc this childDoc belongs to
-        int parentDoc = parentDocs.advance(childDoc);
+        final int parentDoc;
+        if (parentDocs.docID() < childDoc) {
+            parentDoc = parentDocs.advance(childDoc);
+        } else {
+            parentDoc = parentDocs.docID();
+        }
         assert childDoc <= parentDoc && parentDoc != DocIdSetIterator.NO_MORE_DOCS;
         if (bucketOrdToLastCollectedParentDoc.containsKey(bucketOrd)) {
             int lastCollectedParentDoc = bucketOrdToLastCollectedParentDoc.lget();