Fixed issue https://github.com/MongoEngine/mongoengine/issues/442

Added support for pickling BaseQueryset instances
Added BaseQueryset.__getstate__, BaseQuerySet.__setstate__ methods

tests/queryset/pickable.py

@@ -0,0 +1,78 @@
+import pickle
+import unittest
+from pymongo.mongo_client import MongoClient
+from mongoengine import Document, StringField, IntField
+from mongoengine.connection import connect
+
+__author__ = 'stas'
+
+class Person(Document):
+    name = StringField()
+    age = IntField()
+
+class TestQuerysetPickable(unittest.TestCase):
+    """
+    Test for adding pickling support for QuerySet instances
+    See issue https://github.com/MongoEngine/mongoengine/issues/442
+    """
+    def setUp(self):
+        super(TestQuerysetPickable, self).setUp()
+
+        connection = connect(db="test") #type: pymongo.mongo_client.MongoClient
+
+        connection.drop_database("test")
+
+        self.john = Person.objects.create(
+            name="John",
+            age=21
+        )
+
+
+    def test_picke_simple_qs(self):
+
+        qs = Person.objects.all()
+
+        pickle.dumps(qs)
+
+    def _get_loaded(self, qs):
+        s = pickle.dumps(qs)
+
+        return pickle.loads(s)
+
+    def test_unpickle(self):
+        qs = Person.objects.all()
+
+        loadedQs = self._get_loaded(qs)
+
+        self.assertEqual(qs.count(), loadedQs.count())
+
+        #can update loadedQs
+        loadedQs.update(age=23)
+
+        #check
+        self.assertEqual(Person.objects.first().age, 23)
+
+    def test_pickle_support_filtration(self):
+        Person.objects.create(
+            name="Alice",
+            age=22
+        )
+
+        Person.objects.create(
+            name="Bob",
+            age=23
+        )
+
+        qs = Person.objects.filter(age__gte=22)
+        self.assertEqual(qs.count(), 2)
+
+        loaded = self._get_loaded(qs)
+
+        self.assertEqual(loaded.count(), 2)
+        self.assertEqual(loaded.filter(name="Bob").first().age, 23)
+
+
+
+
+
+