fix in librarian

[wolnelektury.git] / apps / newtagging / models.py

diff --git a/apps/newtagging/models.py b/apps/newtagging/models.py
index 56d73bf..694f5b8 100644 (file)
--- a/apps/newtagging/models.py
+++ b/apps/newtagging/models.py
@@ -1,23 +1,20 @@
+# -*- coding: utf-8 -*-

 """
 Models and managers for generic tagging.
 """
 """
 Models and managers for generic tagging.
 """

-# Python 2.3 compatibility
-if not hasattr(__builtins__, 'set'):
-    from sets import Set as set

 
 

-from django.contrib.contenttypes import generic
+from django.contrib.contenttypes.fields import GenericForeignKey

 from django.contrib.contenttypes.models import ContentType
 from django.db import connection, models
 from django.utils.translation import ugettext_lazy as _
 from django.db.models.base import ModelBase
 from django.contrib.contenttypes.models import ContentType
 from django.db import connection, models
 from django.utils.translation import ugettext_lazy as _
 from django.db.models.base import ModelBase

+from django.core.exceptions import ObjectDoesNotExist
+from django.dispatch import Signal

 
 qn = connection.ops.quote_name
 
 
 qn = connection.ops.quote_name
 

-try:
-    from django.db.models.query import parse_lookup
-except ImportError:
-    parse_lookup = None

 
 

+tags_updated = Signal(providing_args=["affected_tags"])

 
 def get_queryset_and_model(queryset_or_model):
     """
 
 def get_queryset_and_model(queryset_or_model):
     """


@@ -40,7 +37,17 @@ class TagManager(models.Manager):
     def __init__(self, intermediary_table_model):
         super(TagManager, self).__init__()
         self.intermediary_table_model = intermediary_table_model
     def __init__(self, intermediary_table_model):
         super(TagManager, self).__init__()
         self.intermediary_table_model = intermediary_table_model

-    
+        models.signals.pre_delete.connect(self.target_deleted)
+
+    def target_deleted(self, instance, **kwargs):
+        """ clear tag relations before deleting an object """
+        try:
+            int(instance.pk)
+        except ValueError:
+            return
+
+        self.update_tags(instance, [])
+

     def update_tags(self, obj, tags):
         """
         Update tags associated with an object.
     def update_tags(self, obj, tags):
         """
         Update tags associated with an object.


@@ -49,7 +56,7 @@ class TagManager(models.Manager):
         current_tags = list(self.filter(items__content_type__pk=content_type.pk,
                                         items__object_id=obj.pk))
         updated_tags = self.model.get_tag_list(tags)
         current_tags = list(self.filter(items__content_type__pk=content_type.pk,
                                         items__object_id=obj.pk))
         updated_tags = self.model.get_tag_list(tags)

-    
+

         # Remove tags which no longer apply
         tags_for_removal = [tag for tag in current_tags \
                             if tag not in updated_tags]
         # Remove tags which no longer apply
         tags_for_removal = [tag for tag in current_tags \
                             if tag not in updated_tags]


@@ -58,10 +65,22 @@ class TagManager(models.Manager):
                                                object_id=obj.pk,
                                                tag__in=tags_for_removal).delete()
         # Add new tags
                                                object_id=obj.pk,
                                                tag__in=tags_for_removal).delete()
         # Add new tags

-        for tag in updated_tags:
+        tags_to_add = [tag for tag in updated_tags
+                       if tag not in current_tags]
+        for tag in tags_to_add:

             if tag not in current_tags:
                 self.intermediary_table_model._default_manager.create(tag=tag, content_object=obj)
             if tag not in current_tags:
                 self.intermediary_table_model._default_manager.create(tag=tag, content_object=obj)

-    
+
+        tags_updated.send(sender=type(obj), instance=obj, affected_tags=tags_to_add + tags_for_removal)
+
+    def remove_tag(self, obj, tag):
+        """
+        Remove tag from an object.
+        """
+        content_type = ContentType.objects.get_for_model(obj)
+        self.intermediary_table_model._default_manager.filter(content_type__pk=content_type.pk,
+            object_id=obj.pk, tag=tag).delete()
+

     def get_for_object(self, obj):
         """
         Create a queryset matching all tags associated with the given
     def get_for_object(self, obj):
         """
         Create a queryset matching all tags associated with the given


@@ -70,65 +89,8 @@ class TagManager(models.Manager):
         ctype = ContentType.objects.get_for_model(obj)
         return self.filter(items__content_type__pk=ctype.pk,
                            items__object_id=obj.pk)
         ctype = ContentType.objects.get_for_model(obj)
         return self.filter(items__content_type__pk=ctype.pk,
                            items__object_id=obj.pk)

-    
-    def _get_usage(self, model, counts=False, min_count=None, extra_joins=None, extra_criteria=None, params=None, extra=None):
-        """
-        Perform the custom SQL query for ``usage_for_model`` and
-        ``usage_for_queryset``.
-        """
-        if min_count is not None: counts = True
-
-        model_table = qn(model._meta.db_table)
-        model_pk = '%s.%s' % (model_table, qn(model._meta.pk.column))
-        tag_columns = self._get_tag_columns()
-        
-        if extra is None: extra = {}
-        extra_where = ''
-        if 'where' in extra:
-            extra_where = 'AND ' + ' AND '.join(extra['where'])
-        
-        query = """
-        SELECT DISTINCT %(tag_columns)s%(count_sql)s
-        FROM
-            %(tag)s
-            INNER JOIN %(tagged_item)s
-                ON %(tag)s.id = %(tagged_item)s.tag_id
-            INNER JOIN %(model)s
-                ON %(tagged_item)s.object_id = %(model_pk)s
-            %%s
-        WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
-            %%s
-            %(extra_where)s
-        GROUP BY %(tag)s.id, %(tag)s.name
-        %%s
-        ORDER BY %(tag)s.%(ordering)s ASC""" % {
-            'tag': qn(self.model._meta.db_table),
-            'ordering': ', '.join(qn(field) for field in self.model._meta.ordering),
-            'tag_columns': tag_columns,
-            'count_sql': counts and (', COUNT(%s)' % model_pk) or '',
-            'tagged_item': qn(self.intermediary_table_model._meta.db_table),
-            'model': model_table,
-            'model_pk': model_pk,
-            'extra_where': extra_where,
-            'content_type_id': ContentType.objects.get_for_model(model).pk,
-        }
-
-        min_count_sql = ''
-        if min_count is not None:
-            min_count_sql = 'HAVING COUNT(%s) >= %%s' % model_pk
-            params.append(min_count)
-
-        cursor = connection.cursor()
-        cursor.execute(query % (extra_joins, extra_criteria, min_count_sql), params)
-        tags = []
-        for row in cursor.fetchall():
-            t = self.model(*row[:len(self.model._meta.fields)])
-            if counts:
-                t.count = row[len(self.model._meta.fields)]
-            tags.append(t)
-        return tags
-
-    def usage_for_model(self, model, counts=False, min_count=None, filters=None, extra=None):
+
+    def usage_for_model(self, model, counts=False, filters=None):

         """
         Obtain a list of tags associated with instances of the given
         Model class.
         """
         Obtain a list of tags associated with instances of the given
         Model class.


@@ -137,39 +99,21 @@ class TagManager(models.Manager):
         each tag, indicating how many times it has been used against
         the Model class in question.
 
         each tag, indicating how many times it has been used against
         the Model class in question.
 

-        If ``min_count`` is given, only tags which have a ``count``
-        greater than or equal to ``min_count`` will be returned.
-        Passing a value for ``min_count`` implies ``counts=True``.
-

         To limit the tags (and counts, if specified) returned to those
         used by a subset of the Model's instances, pass a dictionary
         of field lookups to be applied to the given Model as the
         ``filters`` argument.
         """
         To limit the tags (and counts, if specified) returned to those
         used by a subset of the Model's instances, pass a dictionary
         of field lookups to be applied to the given Model as the
         ``filters`` argument.
         """

-        if extra is None: extra = {}
+        # TODO: Do we really need this filters stuff?

         if filters is None: filters = {}
 
         if filters is None: filters = {}
 

-        if not parse_lookup:
-            # post-queryset-refactor (hand off to usage_for_queryset)
-            queryset = model._default_manager.filter()
-            for f in filters.items():
-                queryset.query.add_filter(f)
-            usage = self.usage_for_queryset(queryset, counts, min_count, extra)
-        else:
-            # pre-queryset-refactor
-            extra_joins = ''
-            extra_criteria = ''
-            params = []
-            if len(filters) > 0:
-                joins, where, params = parse_lookup(filters.items(), model._meta)
-                extra_joins = ' '.join(['%s %s AS %s ON %s' % (join_type, table, alias, condition)
-                                        for (alias, (table, join_type, condition)) in joins.items()])
-                extra_criteria = 'AND %s' % (' AND '.join(where))
-            usage = self._get_usage(model, counts, min_count, extra_joins, extra_criteria, params, extra)
-
+        queryset = model._default_manager.filter()
+        for f in filters.items():
+            queryset.query.add_filter(f)
+        usage = self.usage_for_queryset(queryset, counts)

         return usage
 
         return usage
 

-    def usage_for_queryset(self, queryset, counts=False, min_count=None, extra=None):
+    def usage_for_queryset(self, queryset, counts=False):

         """
         Obtain a list of tags associated with instances of a model
         contained in the given queryset.
         """
         Obtain a list of tags associated with instances of a model
         contained in the given queryset.


@@ -177,23 +121,18 @@ class TagManager(models.Manager):
         If ``counts`` is True, a ``count`` attribute will be added to
         each tag, indicating how many times it has been used against
         the Model class in question.
         If ``counts`` is True, a ``count`` attribute will be added to
         each tag, indicating how many times it has been used against
         the Model class in question.

-
-        If ``min_count`` is given, only tags which have a ``count``
-        greater than or equal to ``min_count`` will be returned.
-        Passing a value for ``min_count`` implies ``counts=True``.

         """
         """

-        if parse_lookup:
-            raise AttributeError("'TagManager.usage_for_queryset' is not compatible with pre-queryset-refactor versions of Django.")
-
-        extra_joins = ' '.join(queryset.query.get_from_clause()[0][1:])
-        where, params = queryset.query.where.as_sql()
-        if where:
-            extra_criteria = 'AND %s' % where
+        usage = self.model._default_manager.filter(
+            items__content_type=ContentType.objects.get_for_model(queryset.model),
+            items__object_id__in=queryset
+            )
+        if counts:
+            usage = usage.annotate(count=models.Count('id'))

         else:
         else:

-            extra_criteria = ''
-        return self._get_usage(queryset.model, counts, min_count, extra_joins, extra_criteria, params, extra)
+            usage = usage.distinct()
+        return usage

 
 

-    def related_for_model(self, tags, model, counts=False, min_count=None, extra=None):
+    def related_for_model(self, tags, model, counts=False):

         """
         Obtain a list of tags related to a given list of tags - that
         is, other tags used by items which have all the given tags.
         """
         Obtain a list of tags related to a given list of tags - that
         is, other tags used by items which have all the given tags.


@@ -201,257 +140,58 @@ class TagManager(models.Manager):
         If ``counts`` is True, a ``count`` attribute will be added to
         each tag, indicating the number of items which have it in
         addition to the given list of tags.
         If ``counts`` is True, a ``count`` attribute will be added to
         each tag, indicating the number of items which have it in
         addition to the given list of tags.

-
-        If ``min_count`` is given, only tags which have a ``count``
-        greater than or equal to ``min_count`` will be returned.
-        Passing a value for ``min_count`` implies ``counts=True``.

         """
         """

-        if min_count is not None: counts = True
-        tags = self.model.get_tag_list(tags)
-        tag_count = len(tags)
-        tagged_item_table = qn(self.intermediary_table_model._meta.db_table)
-        tag_columns = self._get_tag_columns()
-        
-        if extra is None: extra = {}
-        extra_where = ''
-        if 'where' in extra:
-            extra_where = 'AND ' + ' AND '.join(extra['where'])
-        
-        # Temporary table in this query is a hack to prevent MySQL from executing
-        # inner query as dependant query (which could result in severe performance loss)
-        query = """
-        SELECT %(tag_columns)s%(count_sql)s
-        FROM %(tagged_item)s INNER JOIN %(tag)s ON %(tagged_item)s.tag_id = %(tag)s.id
-        WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
-        AND %(tagged_item)s.object_id IN
-        (
-            SELECT temporary.object_id 
-            FROM (
-                SELECT %(tagged_item)s.object_id
-                FROM %(tagged_item)s, %(tag)s
-                WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
-                  AND %(tag)s.id = %(tagged_item)s.tag_id
-                  AND %(tag)s.id IN (%(tag_id_placeholders)s)
-                GROUP BY %(tagged_item)s.object_id
-                HAVING COUNT(%(tagged_item)s.object_id) = %(tag_count)s
-            ) AS temporary
-        )
-        AND %(tag)s.id NOT IN (%(tag_id_placeholders)s)
-        %(extra_where)s
-        GROUP BY %(tag_columns)s
-        %(min_count_sql)s
-        ORDER BY %(tag)s.%(ordering)s ASC""" % {
-            'tag': qn(self.model._meta.db_table),
-            'ordering': ', '.join(qn(field) for field in self.model._meta.ordering),
-            'tag_columns': tag_columns,
-            'count_sql': counts and ', COUNT(%s.object_id)' % tagged_item_table or '',
-            'tagged_item': tagged_item_table,
-            'content_type_id': ContentType.objects.get_for_model(model).pk,
-            'tag_id_placeholders': ','.join(['%s'] * tag_count),
-            'extra_where': extra_where,
-            'tag_count': tag_count,
-            'min_count_sql': min_count is not None and ('HAVING COUNT(%s.object_id) >= %%s' % tagged_item_table) or '',
-        }
-
-        params = [tag.pk for tag in tags] * 2
-        if min_count is not None:
-            params.append(min_count)
-
-        cursor = connection.cursor()
-        cursor.execute(query, params)
-        related = []
-        for row in cursor.fetchall():
-            tag = self.model(*row[:len(self.model._meta.fields)])
-            if counts is True:
-                tag.count = row[len(self.model._meta.fields)]
-            related.append(tag)
-        return related
-
-    def _get_tag_columns(self):
-        tag_table = qn(self.model._meta.db_table)
-        return ', '.join('%s.%s' % (tag_table, qn(field.column)) for field in self.model._meta.fields)
+        objs = self.model.intermediary_table_model.objects.get_by_model(model, tags)
+        qs = self.usage_for_queryset(objs, counts)
+        qs = qs.exclude(pk__in=[tag.pk for tag in tags])
+        return qs

 
 
 class TaggedItemManager(models.Manager):
 
 
 class TaggedItemManager(models.Manager):

-    """
-    FIXME There's currently no way to get the ``GROUP BY`` and ``HAVING``
-          SQL clauses required by many of this manager's methods into
-          Django's ORM.
-
-          For now, we manually execute a query to retrieve the PKs of
-          objects we're interested in, then use the ORM's ``__in``
-          lookup to return a ``QuerySet``.
-
-          Once the queryset-refactor branch lands in trunk, this can be
-          tidied up significantly.
-    """

     def __init__(self, tag_model):
         super(TaggedItemManager, self).__init__()
         self.tag_model = tag_model
     def __init__(self, tag_model):
         super(TaggedItemManager, self).__init__()
         self.tag_model = tag_model

-    
+

     def get_by_model(self, queryset_or_model, tags):
         """
         Create a ``QuerySet`` containing instances of the specified
         model associated with a given tag or list of tags.
         """
     def get_by_model(self, queryset_or_model, tags):
         """
         Create a ``QuerySet`` containing instances of the specified
         model associated with a given tag or list of tags.
         """

-        tags = self.tag_model.get_tag_list(tags)
-        tag_count = len(tags)
-        if tag_count == 0:
-            # No existing tags were given
-            queryset, model = get_queryset_and_model(queryset_or_model)
-            return model._default_manager.none()
-        elif tag_count == 1:
-            # Optimisation for single tag - fall through to the simpler
-            # query below.
-            tag = tags[0]
-        else:
-            return self.get_intersection_by_model(queryset_or_model, tags)
-

         queryset, model = get_queryset_and_model(queryset_or_model)
         queryset, model = get_queryset_and_model(queryset_or_model)

-        content_type = ContentType.objects.get_for_model(model)
-        opts = self.model._meta
-        tagged_item_table = qn(opts.db_table)
-        return queryset.extra(
-            tables=[opts.db_table],
-            where=[
-                '%s.content_type_id = %%s' % tagged_item_table,
-                '%s.tag_id = %%s' % tagged_item_table,
-                '%s.%s = %s.object_id' % (qn(model._meta.db_table),
-                                          qn(model._meta.pk.column),
-                                          tagged_item_table)
-            ],
-            params=[content_type.pk, tag.pk],
-        )
-
-    def get_intersection_by_model(self, queryset_or_model, tags):
-        """
-        Create a ``QuerySet`` containing instances of the specified
-        model associated with *all* of the given list of tags.
-        """

         tags = self.tag_model.get_tag_list(tags)
         tags = self.tag_model.get_tag_list(tags)

-        tag_count = len(tags)
-        queryset, model = get_queryset_and_model(queryset_or_model)
+        if not tags:
+            # No existing tags were given
+            return queryset.none()

 
 

-        if not tag_count:
-            return model._default_manager.none()
-
-        model_table = qn(model._meta.db_table)
-        # This query selects the ids of all objects which have all the
-        # given tags.
-        query = """
-        SELECT %(model_pk)s
-        FROM %(model)s, %(tagged_item)s
-        WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
-          AND %(tagged_item)s.tag_id IN (%(tag_id_placeholders)s)
-          AND %(model_pk)s = %(tagged_item)s.object_id
-        GROUP BY %(model_pk)s
-        HAVING COUNT(%(model_pk)s) = %(tag_count)s""" % {
-            'model_pk': '%s.%s' % (model_table, qn(model._meta.pk.column)),
-            'model': model_table,
-            'tagged_item': qn(self.model._meta.db_table),
-            'content_type_id': ContentType.objects.get_for_model(model).pk,
-            'tag_id_placeholders': ','.join(['%s'] * tag_count),
-            'tag_count': tag_count,
-        }
-
-        cursor = connection.cursor()
-        cursor.execute(query, [tag.pk for tag in tags])
-        object_ids = [row[0] for row in cursor.fetchall()]
-        if len(object_ids) > 0:
-            return queryset.filter(pk__in=object_ids)
-        else:
-            return model._default_manager.none()
+        # TODO: presumes reverse generic relation
+        # Multiple joins are WAY faster than having-count, at least on Postgres 9.1.
+        for tag in tags:
+            queryset = queryset.filter(tag_relations__tag=tag)
+        return queryset

 
     def get_union_by_model(self, queryset_or_model, tags):
         """
         Create a ``QuerySet`` containing instances of the specified
         model associated with *any* of the given list of tags.
         """
 
     def get_union_by_model(self, queryset_or_model, tags):
         """
         Create a ``QuerySet`` containing instances of the specified
         model associated with *any* of the given list of tags.
         """

-        tags = self.tag_model.get_tag_list(tags)
-        tag_count = len(tags)

         queryset, model = get_queryset_and_model(queryset_or_model)
         queryset, model = get_queryset_and_model(queryset_or_model)

+        tags = self.tag_model.get_tag_list(tags)
+        if not tags:
+            return queryset.none()
+        # TODO: presumes reverse generic relation
+        return queryset.filter(tag_relations__tag__in=tags).distinct()

 
 

-        if not tag_count:
-            return model._default_manager.none()
-
-        model_table = qn(model._meta.db_table)
-        # This query selects the ids of all objects which have any of
-        # the given tags.
-        query = """
-        SELECT %(model_pk)s
-        FROM %(model)s, %(tagged_item)s
-        WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
-          AND %(tagged_item)s.tag_id IN (%(tag_id_placeholders)s)
-          AND %(model_pk)s = %(tagged_item)s.object_id
-        GROUP BY %(model_pk)s""" % {
-            'model_pk': '%s.%s' % (model_table, qn(model._meta.pk.column)),
-            'model': model_table,
-            'tagged_item': qn(self.model._meta.db_table),
-            'content_type_id': ContentType.objects.get_for_model(model).pk,
-            'tag_id_placeholders': ','.join(['%s'] * tag_count),
-        }
-
-        cursor = connection.cursor()
-        cursor.execute(query, [tag.pk for tag in tags])
-        object_ids = [row[0] for row in cursor.fetchall()]
-        if len(object_ids) > 0:
-            return queryset.filter(pk__in=object_ids)
-        else:
-            return model._default_manager.none()
-
-    def get_related(self, obj, queryset_or_model, num=None):
+    def get_related(self, obj, queryset_or_model):

         """
         Retrieve a list of instances of the specified model which share
         tags with the model instance ``obj``, ordered by the number of
         shared tags in descending order.
         """
         Retrieve a list of instances of the specified model which share
         tags with the model instance ``obj``, ordered by the number of
         shared tags in descending order.

-
-        If ``num`` is given, a maximum of ``num`` instances will be
-        returned.

         """
         queryset, model = get_queryset_and_model(queryset_or_model)
         """
         queryset, model = get_queryset_and_model(queryset_or_model)

-        model_table = qn(model._meta.db_table)
-        content_type = ContentType.objects.get_for_model(obj)
-        related_content_type = ContentType.objects.get_for_model(model)
-        query = """
-        SELECT %(model_pk)s, COUNT(related_tagged_item.object_id) AS %(count)s
-        FROM %(model)s, %(tagged_item)s, %(tag)s, %(tagged_item)s related_tagged_item
-        WHERE %(tagged_item)s.object_id = %%s
-          AND %(tagged_item)s.content_type_id = %(content_type_id)s
-          AND %(tag)s.id = %(tagged_item)s.tag_id
-          AND related_tagged_item.content_type_id = %(related_content_type_id)s
-          AND related_tagged_item.tag_id = %(tagged_item)s.tag_id
-          AND %(model_pk)s = related_tagged_item.object_id"""
-        if content_type.pk == related_content_type.pk:
-            # Exclude the given instance itself if determining related
-            # instances for the same model.
-            query += """
-          AND related_tagged_item.object_id != %(tagged_item)s.object_id"""
-        query += """
-        GROUP BY %(model_pk)s
-        ORDER BY %(count)s DESC
-        %(limit_offset)s"""
-        query = query % {
-            'model_pk': '%s.%s' % (model_table, qn(model._meta.pk.column)),
-            'count': qn('count'),
-            'model': model_table,
-            'tagged_item': qn(self.model._meta.db_table),
-            'tag': qn(self.model._meta.get_field('tag').rel.to._meta.db_table),
-            'content_type_id': content_type.pk,
-            'related_content_type_id': related_content_type.pk,
-            'limit_offset': num is not None and connection.ops.limit_offset_sql(num) or '',
-        }
-
-        cursor = connection.cursor()
-        cursor.execute(query, [obj.pk])
-        object_ids = [row[0] for row in cursor.fetchall()]
-        if len(object_ids) > 0:
-            # Use in_bulk here instead of an id__in lookup, because id__in would
-            # clobber the ordering.
-            object_dict = queryset.in_bulk(object_ids)
-            return [object_dict[object_id] for object_id in object_ids \
-                    if object_id in object_dict]
-        else:
-            return []
+        # TODO: presumes reverse generic relation.
+        # Do we know it's 'tags'?
+        return queryset.filter(tag_relations__tag__in=obj.tags).annotate(
+            count=models.Count('pk')).order_by('-count').exclude(pk=obj.pk)

 
 
 ##########
 
 
 ##########


@@ -460,22 +200,26 @@ class TaggedItemManager(models.Manager):
 def create_intermediary_table_model(model):
     """Create an intermediary table model for the specific tag model"""
     name = model.__name__ + 'Relation'
 def create_intermediary_table_model(model):
     """Create an intermediary table model for the specific tag model"""
     name = model.__name__ + 'Relation'

-     
+

     class Meta:
         db_table = '%s_relation' % model._meta.db_table
         unique_together = (('tag', 'content_type', 'object_id'),)
     class Meta:
         db_table = '%s_relation' % model._meta.db_table
         unique_together = (('tag', 'content_type', 'object_id'),)

+        app_label = model._meta.app_label

 
     def obj_unicode(self):
 
     def obj_unicode(self):

-        return u'%s [%s]' % (self.content_type.get_object_for_this_type(pk=self.object_id), self.tag)
-        
-    # Set up a dictionary to simulate declarations within a class    
+        try:
+            return u'%s [%s]' % (self.content_type.get_object_for_this_type(pk=self.object_id), self.tag)
+        except ObjectDoesNotExist:
+            return u'<deleted> [%s]' % self.tag
+
+    # Set up a dictionary to simulate declarations within a class

     attrs = {
         '__module__': model.__module__,
         'Meta': Meta,
         'tag': models.ForeignKey(model, verbose_name=_('tag'), related_name='items'),
         'content_type': models.ForeignKey(ContentType, verbose_name=_('content type')),
         'object_id': models.PositiveIntegerField(_('object id'), db_index=True),
     attrs = {
         '__module__': model.__module__,
         'Meta': Meta,
         'tag': models.ForeignKey(model, verbose_name=_('tag'), related_name='items'),
         'content_type': models.ForeignKey(ContentType, verbose_name=_('content type')),
         'object_id': models.PositiveIntegerField(_('object id'), db_index=True),

-        'content_object': generic.GenericForeignKey('content_type', 'object_id'),
+        'content_object': GenericForeignKey('content_type', 'object_id'),

         '__unicode__': obj_unicode,
     }
 
         '__unicode__': obj_unicode,
     }
 


@@ -484,8 +228,8 @@ def create_intermediary_table_model(model):
 
 class TagMeta(ModelBase):
     "Metaclass for tag models (models inheriting from TagBase)."
 
 class TagMeta(ModelBase):
     "Metaclass for tag models (models inheriting from TagBase)."

-    def __new__(cls, name, bases, attrs):
-        model = super(TagMeta, cls).__new__(cls, name, bases, attrs)
+    def __new__(mcs, name, bases, attrs):
+        model = super(TagMeta, mcs).__new__(mcs, name, bases, attrs)

         if not model._meta.abstract:
             # Create an intermediary table and register custom managers for concrete models
             model.intermediary_table_model = create_intermediary_table_model(model)
         if not model._meta.abstract:
             # Create an intermediary table and register custom managers for concrete models
             model.intermediary_table_model = create_intermediary_table_model(model)


@@ -497,15 +241,15 @@ class TagMeta(ModelBase):
 class TagBase(models.Model):
     """Abstract class to be inherited by model classes."""
     __metaclass__ = TagMeta
 class TagBase(models.Model):
     """Abstract class to be inherited by model classes."""
     __metaclass__ = TagMeta

-    
+

     class Meta:
         abstract = True
     class Meta:
         abstract = True

-    
+

     @staticmethod
     def get_tag_list(tag_list):
         """
         Utility function for accepting tag input in a flexible manner.
     @staticmethod
     def get_tag_list(tag_list):
         """
         Utility function for accepting tag input in a flexible manner.

-        
+

         You should probably override this method in your subclass.
         """
         if isinstance(tag_list, TagBase):
         You should probably override this method in your subclass.
         """
         if isinstance(tag_list, TagBase):