Changeset 7499

Timestamp:

04/28/08 09:14:41 (1 year ago)

Author:

mtredinnick

Message:

Added the ability to pickle and unpickle QuerySets? and Query classes.

Files:

• django/trunk/django/db/models/query.py (modified) (2 diffs)
• django/trunk/django/db/models/sql/query.py (modified) (1 diff)
• django/trunk/docs/db-api.txt (modified) (1 diff)

django/trunk/django/db/models/query.py

@@ -29 +29 @@
-    ########################
-
+    def __getstate__(self):
+        """
+        Allows the Queryset to be pickled.
+        """
+        # Force the cache to be fully populated.
+        len(self)
+
+        obj_dict = self.__dict__.copy()
+        obj_dict['_iter'] = None
+        return obj_dict
+
-    def __repr__(self):
-        return repr(list(self))
@@ -38 +49 @@
-        if self._result_cache is None:
-            if self._iter:
-()
+
-            else:
-                self._result_cache = list(self.iterator())

django/trunk/django/db/models/sql/query.py

@@ -99 +99 @@
-        memo[id(self)] = result
-        return result
+
+    def __getstate__(self):
+        """
+        Pickling support.
+        """
+        obj_dict = self.__dict__.copy()
+        del obj_dict['connection']
+        return obj_dict
+
+    def __setstate__(self, obj_dict):
+        """
+        Unpickling support.
+        """
+        self.__dict__.update(obj_dict)
+        # XXX: Need a better solution for this when multi-db stuff is
+        # supported. It's the only class-reference to the module-level
+        # connection variable.
+        self.connection = connection
-
-    def get_meta(self):

django/trunk/docs/db-api.txt

@@ -376 +376 @@
-      iterating over a ``QuerySet`` will take advantage of your database to
-      load data and instantiate objects only as you need them.
+
+
+Pickling QuerySets
+~~~~~~~~~~~~~~~~~~
+
+If you pickle_ a ``QuerySet``, this will also force all the results to be
+loaded into memory prior to pickling. This is because pickling is usually used
+as a precursor to caching and when the cached queryset is reloaded, you want
+the results to already be present. This means that when you unpickle a
+``QuerySet``, it contains the results at the moment it was pickled, rather
+than the results that are currently in the database.
+
+If you only want to pickle the necessary information to recreate the
+``Queryset`` from the database at a later time, pickle the ``query`` attribute
+of the ``QuerySet``. You can then recreate the original ``QuerySet`` (without
+any results loaded) using some code like this::
+
+    >>> import pickle
+    >>> query = pickle.loads(s)     # Assuming 's' is the pickled string.
+    >>> qs = MyModel.objects.all()
+    >>> qs.query = query            # Restore the original 'query'.
+
+.. _pickle: http://docs.python.org/lib/module-pickle.html
-
-Limiting QuerySets