Improved cache system

piranna · piranna · commit 3a7da1ca3402 · 2012-05-19T23:35:39.000+02:00
diff --git a/sqlparse/utils.py b/sqlparse/utils.py
@@ -4,6 +4,60 @@
 @author: piranna
 '''
 
+try:
+    from collections import OrderedDict
+except ImportError:
+    OrderedDict = None
+
+
+if OrderedDict:
+    class Cache(OrderedDict):
+        """Cache with LRU algorithm using an OrderedDict as basis
+        """
+        def __init__(self, maxsize=100):
+            OrderedDict.__init__(self)
+
+            self._maxsize = maxsize
+
+        def __getitem__(self, key, *args, **kwargs):
+            # Remove the (key, value) pair from the cache, or raise KeyError
+            value = self.pop(key)
+
+            # Insert the (key, value) pair on the front of the cache
+            OrderedDict.__setitem__(self, key, value)
+
+            # Return the value from the cache
+            return value
+
+        def __setitem__(self, key, value, *args, **kwargs):
+            # Key was inserted before, remove it so we put it at front later
+            if key in self:
+                del self[key]
+
+            # Too much items on the cache, remove the least recent used
+            elif len(self) >= self._maxsize:
+                self.popitem(False)
+
+            # Insert the (key, value) pair on the front of the cache
+            OrderedDict.__setitem__(self, key, value, *args, **kwargs)
+
+else:
+    class Cache(dict):
+        """Cache that reset when gets full
+        """
+        def __init__(self, maxsize=100):
+            dict.__init__(self)
+
+            self._maxsize = maxsize
+
+        def __setitem__(self, key, value, *args, **kwargs):
+            # Reset the cache if we have too much cached entries and start over
+            if len(self) >= self._maxsize:
+                self.clear()
+
+            # Insert the (key, value) pair on the front of the cache
+            dict.__setitem__(self, key, value, *args, **kwargs)
+
 
 def memoize_generator(func):
     """Memoize decorator for generators
@@ -13,7 +67,7 @@ def memoize_generator(func):
     Obviusly, this is only useful if the generator will always return the same
     values for each specific parameters...
     """
-    cache = {}
+    cache = Cache()
 
     def wrapped_func(*args, **kwargs):
 #        params = (args, kwargs)
@@ -26,12 +80,6 @@ def wrapped_func(*args, **kwargs):
 
         # Not cached, exec and store it
         except KeyError:
-            # Reset the cache if we have too much cached entries and start over
-            # In the future would be better to use an OrderedDict and drop the
-            # Least Recent Used entries
-            if len(cache) >= 10:
-                cache.clear()
-
             cached = []
 
             for item in func(*args, **kwargs):
