diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
index f8780ce57d..5b72dbd24a 100644
--- a/src/backend/catalog/partition.c
+++ b/src/backend/catalog/partition.c
@@ -123,7 +123,9 @@ get_partition_parent_worker(Relation inhRel, Oid relid, bool *detach_pending)
  * get_partition_ancestors
  *		Obtain ancestors of given relation
  *
- * Returns a list of ancestors of the given relation.
+ * Returns a list of ancestors of the given relation.  The list is ordered:
+ * The first element is the immediate parent and the last one is the topmost
+ * parent in the partition hierarchy.
  *
  * Note: Because this function assumes that the relation whose OID is passed
  * as an argument and each ancestor will have precisely one parent, it should