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],
)
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 []
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()