From 2d9b581f34324ac2759452fb5a839282ca35f361 Mon Sep 17 00:00:00 2001
From: Shaun Duncan <shaun.duncan@coxinc.com>
Date: Fri, 15 Jun 2012 15:42:19 -0400
Subject: [PATCH] Adding check if cascade delete is self-referencing. If so,
 prevent recursing if there are no objects to evaluate

---
 mongoengine/queryset.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mongoengine/queryset.py b/mongoengine/queryset.py
index 1fb3eda7..8370d333 100644
--- a/mongoengine/queryset.py
+++ b/mongoengine/queryset.py
@@ -1314,7 +1314,9 @@ class QuerySet(object):
             document_cls, field_name = rule_entry
             rule = doc._meta['delete_rules'][rule_entry]
             if rule == CASCADE:
-                document_cls.objects(**{field_name + '__in': self}).delete(safe=safe)
+                ref_q = document_cls.objects(**{field_name + '__in': self})
+                if doc != document_cls or (doc == document_cls and ref_q.count() > 0):
+                    ref_q.delete(safe=safe)
             elif rule == NULLIFY:
                 document_cls.objects(**{field_name + '__in': self}).update(
                         safe_update=safe,