change the weakkeydict to be just an LRU cache. Add tests

for the "many combinations of UPDATE keys" issue.

2 files changed, 57 insertions, 4 deletions

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 94e969bcc..4df51928b 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -43,6 +43,7 @@ _new_mappers = False
 _already_compiling = False
 _none_set = frozenset([None])
 
+
 # a list of MapperExtensions that will be installed in all mappers by default
 global_extensions = []
 
@@ -97,7 +98,9 @@ class Mapper(object):
                  include_properties=None,
                  exclude_properties=None,
                  passive_updates=True,
-                 eager_defaults=False):
+                 eager_defaults=False,
+                 _compiled_cache_size=100,
+                 ):
         """Construct a new mapper.
 
         Mappers are normally constructed via the :func:`~sqlalchemy.orm.mapper`
@@ -140,6 +143,7 @@ class Mapper(object):
         self._requires_row_aliasing = False
         self._inherits_equated_pairs = None
         self._memoized_values = {}
+        self._compiled_cache_size = _compiled_cache_size
         
         if allow_null_pks:
             util.warn_deprecated('the allow_null_pks option to Mapper() is '
@@ -1264,7 +1268,7 @@ class Mapper(object):
 
     @util.memoized_property
     def _compiled_cache(self):
-        return weakref.WeakKeyDictionary()
+        return util.LRUCache(self._compiled_cache_size)
 
     @util.memoized_property
     def _sorted_tables(self):
@@ -1342,7 +1346,7 @@ class Mapper(object):
 
         cached_connections = util.PopulateDict(
             lambda conn:conn.execution_options(
-            compiled_cache=self._compiled_cache.setdefault(conn.engine, {})
+            compiled_cache=self._compiled_cache
         ))
 
         # if session has a connection callable,
@@ -1740,7 +1744,7 @@ class Mapper(object):
         tups = []
         cached_connections = util.PopulateDict(
             lambda conn:conn.execution_options(
-            compiled_cache=self._compiled_cache.setdefault(conn.engine, {})
+            compiled_cache=self._compiled_cache
         ))
         
         for state in _sort_states(states):
diff --git a/lib/sqlalchemy/util.py b/lib/sqlalchemy/util.py
index c2c85a4c9..4b04901a1 100644
--- a/lib/sqlalchemy/util.py
+++ b/lib/sqlalchemy/util.py
@@ -19,6 +19,7 @@ except ImportError:
 
 py3k = getattr(sys, 'py3kwarning', False) or sys.version_info >= (3, 0)
 jython = sys.platform.startswith('java')
+win32 = sys.platform.startswith('win')
 
 if py3k:
     set_types = set
@@ -1542,6 +1543,54 @@ class WeakIdentityMapping(weakref.WeakKeyDictionary):
     def _ref(self, object):
         return self._keyed_weakref(object, self._cleanup)
 
+import time
+if win32 or jython:
+    time_func = time.clock
+else:
+    time_func = time.time 
+
+class LRUCache(dict):
+    def __init__(self, capacity=100, threshold=.5):
+        self.capacity = capacity
+        self.threshold = threshold
+
+    def __getitem__(self, key):
+        item = dict.__getitem__(self, key)
+        item[2] = time_func()
+        return item[1]
+
+    def values(self):
+        return [i[1] for i in dict.values(self)]
+
+    def setdefault(self, key, value):
+        if key in self:
+            return self[key]
+        else:
+            self[key] = value
+            return value
+
+    def __setitem__(self, key, value):
+        item = dict.get(self, key)
+        if item is None:
+            item = [key, value, time_func()]
+            dict.__setitem__(self, key, item)
+        else:
+            item[1] = value
+        self._manage_size()
+
+    def _manage_size(self):
+        while len(self) > self.capacity + self.capacity * self.threshold:
+            bytime = sorted(dict.values(self), 
+                            key=operator.itemgetter(2),
+                            reverse=True)
+            for item in bytime[self.capacity:]:
+                try:
+                    del self[item[0]]
+                except KeyError:
+                    # if we couldnt find a key, most 
+                    # likely some other thread broke in 
+                    # on us. loop around and try again
+                    break
 
 def warn(msg, stacklevel=3):
     if isinstance(msg, basestring):