- add workaround for sqlite memusage tests, so no longer need to count to 220/skip tests

- Fixed potential memory leak which could occur if an
arbitrary number of :class:`.sessionmaker` objects
were created.   The anonymous subclass created by
the sessionmaker, when dereferenced, would not be garbage
collected due to remaining class-level references from the
event package.  This issue also applies to any custom system
that made use of ad-hoc subclasses in conjunction with
an event dispatcher.  Also in 0.7.10. [ticket:2650]

1 files changed, 13 insertions, 4 deletions

diff --git a/lib/sqlalchemy/event.py b/lib/sqlalchemy/event.py
index 6293572a3..f28f19ee9 100644
--- a/lib/sqlalchemy/event.py
+++ b/lib/sqlalchemy/event.py
@@ -8,6 +8,7 @@
 
 from . import util, exc
 from itertools import chain
+import weakref
 
 CANCEL = util.symbol('CANCEL')
 NO_RETVAL = util.symbol('NO_RETVAL')
@@ -242,11 +243,12 @@ class _DispatchDescriptor(object):
     def __init__(self, fn):
         self.__name__ = fn.__name__
         self.__doc__ = fn.__doc__
-        self._clslevel = util.defaultdict(list)
-        self._empty_listeners = {}
+        self._clslevel = weakref.WeakKeyDictionary()
+        self._empty_listeners = weakref.WeakKeyDictionary()
 
     def _contains(self, cls, evt):
-        return evt in self._clslevel[cls]
+        return cls in self._clslevel and \
+            evt in self._clslevel[cls]
 
     def insert(self, obj, target, propagate):
         assert isinstance(target, type), \
@@ -258,6 +260,8 @@ class _DispatchDescriptor(object):
             if cls is not target and cls not in self._clslevel:
                 self.update_subclass(cls)
             else:
+                if cls not in self._clslevel:
+                    self._clslevel[cls] = []
                 self._clslevel[cls].insert(0, obj)
 
     def append(self, obj, target, propagate):
@@ -271,9 +275,13 @@ class _DispatchDescriptor(object):
             if cls is not target and cls not in self._clslevel:
                 self.update_subclass(cls)
             else:
+                if cls not in self._clslevel:
+                    self._clslevel[cls] = []
                 self._clslevel[cls].append(obj)
 
     def update_subclass(self, target):
+        if target not in self._clslevel:
+            self._clslevel[target] = []
         clslevel = self._clslevel[target]
         for cls in target.__mro__[1:]:
             if cls in self._clslevel:
@@ -288,7 +296,8 @@ class _DispatchDescriptor(object):
         while stack:
             cls = stack.pop(0)
             stack.extend(cls.__subclasses__())
-            self._clslevel[cls].remove(obj)
+            if cls in self._clslevel:
+                self._clslevel[cls].remove(obj)
 
     def clear(self):
         """Clear all class level listeners"""