Ticket #4831: 4831-1.diff

django/core/cache/backends/simple.py

@@ -21 +21 @@
-        except (ValueError, TypeError):
-            self._cull_frequency = 3
-
+    def add(self, key, value, timeout=None):
+        if len(self._cache) >= self._max_entries:
+            self._cull()
+        if timeout is None:
+            timeout = self.default_timeout
+        if key not in self._cache.keys():
+            self._cache[key] = value
+            self._expire_info[key] = time.time() + timeout
+
-    def get(self, key, default=None):
-        now = time.time()
-        exp = self._expire_info.get(key)

django/core/cache/backends/base.py

@@ -14 +14 @@
-            timeout = 300
-        self.default_timeout = timeout
-
+    def add(self, key, value, timeout=None):
+        """
+        Set a value in the cache if the key does not already exist.  If
+        timeout is given, that timeout will be used for the key; otherwise
+        the default cache timeout will be used.
+        """
+        raise NotImplementedError
+
-    def get(self, key, default=None):
-        """
-        Fetch a given key from the cache.  If the key does not exist, return

django/core/cache/backends/dummy.py

@@ -6 +6 @@
-    def __init__(self, *args, **kwargs):
-        pass
-
+    def add(self, *args, **kwargs):
+        pass
+
-    def get(self, key, default=None):
-        return default
-

django/core/cache/backends/locmem.py

@@ -9 +9 @@
-        SimpleCacheClass.__init__(self, host, params)
-        self._lock = RWLock()
-
+    def add(self, key, value, timeout=None):
+        self._lock.writer_enters()
+        try:
+            SimpleCacheClass.add(self, key, value, timeout)
+        finally:
+            self._lock.writer_leaves()
+
-    def get(self, key, default=None):
-        should_delete = False
-        self._lock.reader_enters()

django/core/cache/backends/filebased.py

@@ -16 +16 @@
-        del self._cache
-        del self._expire_info
-
+    def add(self, key, value, timeout=None):
+        fname = self._key_to_file(key)
+        if timeout is None:
+            timeout = self.default_timeout
+        try:
+            filelist = os.listdir(self._dir)
+        except (IOError, OSError):
+            self._createdir()
+            filelist = []
+        if len(filelist) > self._max_entries:
+            self._cull(filelist)
+        if os.path.basename(fname) not in filelist:
+            try:
+                f = open(fname, 'wb')
+                now = time.time()
+                pickle.dump(now + timeout, f, 2)
+                pickle.dump(value, f, 2)
+            except (IOError, OSError):
+                pass
+
-    def get(self, key, default=None):
-        fname = self._key_to_file(key)
-        try:

django/core/cache/backends/db.py

@@ -24 +24 @@
-        except (ValueError, TypeError):
-            self._cull_frequency = 3
-
+    def add(self, key, value, timeout=None):
+        return self._base_set('add', key, value, timeout)
+
-    def get(self, key, default=None):
-        cursor = connection.cursor()
-        cursor.execute("SELECT cache_key, value, expires FROM %s WHERE cache_key = %%s" % self._table, [key])
@@ -38 +41 @@
-        return pickle.loads(base64.decodestring(row[1]))
-
-    def set(self, key, value, timeout=None):
+        return self._base_set('set', key, value, timeout)
+
+    def delete(self, key):
+        cursor = connection.cursor()
+        cursor.execute("DELETE FROM %s WHERE cache_key = %%s" % self._table, [key])
+        transaction.commit_unless_managed()
+
+    def has_key(self, key):
+        cursor = connection.cursor()
+        cursor.execute("SELECT cache_key FROM %s WHERE cache_key = %%s" % self._table, [key])
+        return cursor.fetchone() is not None
+
+    def _base_set(self, mode, key, value, timeout=None):
-        if timeout is None:
-            timeout = self.default_timeout
-        cursor = connection.cursor()
@@ -50 +66 @@
-        encoded = base64.encodestring(pickle.dumps(value, 2)).strip()
-        cursor.execute("SELECT cache_key FROM %s WHERE cache_key = %%s" % self._table, [key])
-        try:
-
+mode == 'set' and 
-                cursor.execute("UPDATE %s SET value = %%s, expires = %%s WHERE cache_key = %%s" % self._table, [encoded, str(exp), key])
-            else:
-
+
+
-        except DatabaseError:
-            # To be threadsafe, updates/inserts are allowed to fail silently
-            pass
-        else:
-            transaction.commit_unless_managed()
-
-    def delete(self, key):
-        cursor = connection.cursor()
-        cursor.execute("DELETE FROM %s WHERE cache_key = %%s" % self._table, [key])
-        transaction.commit_unless_managed()
-
-    def has_key(self, key):
-        cursor = connection.cursor()
-        cursor.execute("SELECT cache_key FROM %s WHERE cache_key = %%s" % self._table, [key])
-        return cursor.fetchone() is not None
-
-    def _cull(self, cursor, now):
-        if self._cull_frequency == 0:
-            cursor.execute("DELETE FROM %s" % self._table)

django/core/cache/backends/memcached.py

@@ -15 +15 @@
-        BaseCache.__init__(self, params)
-        self._cache = memcache.Client(server.split(';'))
-
+    def add(self, key, value, timeout=0):
+        self._cache.add(key.encode('ascii', 'ignore'), value, timeout or self.default_timeout)
+
-    def get(self, key, default=None):
-        val = self._cache.get(key)
-        if val is None:

tests/regressiontests/cache/tests.py

@@ -17 +17 @@
-        cache.set("key", "value")
-        self.assertEqual(cache.get("key"), "value")
-
+    def test_add(self):
+        # test add (only add if key isn't already in cache)
+        cache.add("addkey1", "value")
+        cache.add("addkey1", "newvalue")
+        self.assertEqual(cache.get("addkey1"), "value")
+
-    def test_non_existent(self):
-        # get with non-existent keys
-        self.assertEqual(cache.get("does not exist"), None)

docs/cache.txt

@@ -324 +324 @@
-    >>> cache.get('my_key', 'has expired')
-    'has expired'
-
+To add a key only if it doesn't already exist, there is an add() method.  It
+takes the same parameters as set(), but will not attempt to update the cache
+if the key specified is already present::
+
+    >>> cache.set('add_key', 'Initial value')
+    >>> cache.add('add_key', 'New value')
+    >>> cache.get('add_key')
+    'Initial value'
+
-There's also a get_many() interface that only hits the cache once. get_many()
-returns a dictionary with all the keys you asked for that actually exist in the
-cache (and haven't expired)::