Ejemplo n.º 1
0
    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 = 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)
        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],
        )
Ejemplo n.º 2
0
    def get_related(self, obj, queryset_or_model, num=None):
        """
        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)
        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,
            # Hardcoding this for now just to get tests working again - this
            # should now be handled by the query object.
            'limit_offset': num is not None and 'LIMIT %s' or '',
        }

        cursor = connection.cursor()
        params = [obj.pk]
        if num is not None:
            params.append(num)
        cursor.execute(query, params)
        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 []
Ejemplo n.º 3
0
    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 = get_tag_list(tags)
        tag_count = len(tags)
        queryset, model = get_queryset_and_model(queryset_or_model)

        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()