commit 395fd75a6e9845bca9f32af51a4dbfe666aba5ff
Author: Amit Khandekar <amit.khandekar@enterprisedb.com>
Date:   Thu Jun 21 11:45:19 2018 +0530

    Correctly use the return value of list_concat

diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index e190ad4..dbf9adc 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -1274,7 +1274,7 @@ create_append_path(PlannerInfo *root,
 	pathnode->first_partial_path = list_length(subpaths);
 	pathnode->subpaths = list_concat(subpaths, partial_subpaths);
 
-	foreach(l, subpaths)
+	foreach(l, pathnode->subpaths)
 	{
 		Path	   *subpath = (Path *) lfirst(l);