def annotate_with_comment_count(queryset):
"""
Annotate queryset with comment count
From: http://djangosnippets.org/snippets/1101/
"""
commented_model = queryset.model
contenttype = ContentType.objects.get_for_model(commented_model)
commented_table = commented_model._meta.db_table
comment_table = Comment._meta.db_table
# NOTE: ::text is specific to PostgreSQL
sql = 'SELECT COUNT(*) FROM %s WHERE %s=%%s AND %s=%s::text' % (
_qn(comment_table),
_qf(comment_table, 'content_type_id'),
_qf(comment_table, 'object_pk'),
_qf(commented_table, 'id')
)
return queryset.extra(select={'comment_count': sql},
select_params=(contenttype.pk,))
def _qf(table, field): # quote table and field
return '{}.{}'.format(_qn(table), _qn(field))
