Behave properly on empty search.

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

diff --git a/apps/newtagging/models.py b/apps/newtagging/models.py
index 5385e95..2055ec3 100644 (file)
--- a/apps/newtagging/models.py
+++ b/apps/newtagging/models.py
@@ -1,8 +1,12 @@
+# -*- coding: utf-8 -*-
 """
 Models and managers for generic tagging.
 """
+
 # Python 2.3 compatibility
-if not hasattr(__builtins__, 'set'):
+try:
+    set
+except NameError: 
     from sets import Set as set
 
 from django.contrib.contenttypes import generic
@@ -10,6 +14,7 @@ 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
 
 qn = connection.ops.quote_name
 
@@ -62,6 +67,14 @@ class TagManager(models.Manager):
             if tag not in current_tags:
                 self.intermediary_table_model._default_manager.create(tag=tag, content_object=obj)
     
+    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
@@ -99,7 +112,7 @@ class TagManager(models.Manager):
         WHERE %(tagged_item)s.content_type_id = %(content_type_id)s
             %%s
             %(extra_where)s
-        GROUP BY %(tag)s.id, %(tag)s.name
+        GROUP BY %(tag_columns)s, %(tag)s.id, %(tag)s.name
         %%s
         ORDER BY %(tag)s.%(ordering)s ASC""" % {
             'tag': qn(self.model._meta.db_table),
@@ -217,22 +230,27 @@ class TagManager(models.Manager):
         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 %(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
-          )
-          AND %(tag)s.id NOT IN (%(tag_id_placeholders)s)
-          %(extra_where)s
+        AND %(tagged_item)s.object_id IN
+        (
+            SELECT *
+            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""" % {
@@ -461,8 +479,11 @@ def create_intermediary_table_model(model):
         unique_together = (('tag', 'content_type', 'object_id'),)
 
     def obj_unicode(self):
-        return u'%s [%s]' % (self.content_type.get_object_for_this_type(pk=self.object_id), self.tag)
-        
+        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__,