- add MemoizedSlots, a generalized solution to using __getattr__

for memoization on a class that uses slots.
- apply many more __slots__.  mem use for nova now at 46% savings

1 files changed, 43 insertions, 0 deletions

diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index b708665f9..22b6ad4ca 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -522,6 +522,15 @@ class portable_instancemethod(object):
 
     """
 
+    __slots__ = 'target', 'name', '__weakref__'
+
+    def __getstate__(self):
+        return {'target': self.target, 'name': self.name}
+
+    def __setstate__(self, state):
+        self.target = state['target']
+        self.name = state['name']
+
     def __init__(self, meth):
         self.target = meth.__self__
         self.name = meth.__name__
@@ -800,6 +809,40 @@ class group_expirable_memoized_property(object):
         return memoized_instancemethod(fn)
 
 
+class MemoizedSlots(object):
+    """Apply memoized items to an object using a __getattr__ scheme.
+
+    This allows the functionality of memoized_property and
+    memoized_instancemethod to be available to a class using __slots__.
+
+    """
+
+    def _fallback_getattr(self, key):
+        raise AttributeError(key)
+
+    def __getattr__(self, key):
+        if key.startswith('_memoized'):
+            raise AttributeError(key)
+        elif hasattr(self, '_memoized_attr_%s' % key):
+            value = getattr(self, '_memoized_attr_%s' % key)()
+            setattr(self, key, value)
+            return value
+        elif hasattr(self, '_memoized_method_%s' % key):
+            fn = getattr(self, '_memoized_method_%s' % key)
+
+            def oneshot(*args, **kw):
+                result = fn(*args, **kw)
+                memo = lambda *a, **kw: result
+                memo.__name__ = fn.__name__
+                memo.__doc__ = fn.__doc__
+                setattr(self, key, memo)
+                return result
+            oneshot.__doc__ = fn.__doc__
+            return oneshot
+        else:
+            return self._fallback_getattr(key)
+
+
 def dependency_for(modulename):
     def decorate(obj):
         # TODO: would be nice to improve on this import silliness,