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2017-05-24 11:33:11 -04:00

33 lines
1.2 KiB
Python

from __future__ import unicode_literals
from django.db.models import Manager
class NaturalOrderByManager(Manager):
def natural_order_by(self, *fields):
"""
Attempt to order records naturally by segmenting a field into three parts:
1. Leading integer (if any)
2. Middle portion
3. Trailing integer (if any)
:param fields: The fields on which to order the queryset. The last field in the list will be ordered naturally.
"""
db_table = self.model._meta.db_table
primary_field = fields[-1]
id1 = '_{}_{}1'.format(db_table, primary_field)
id2 = '_{}_{}2'.format(db_table, primary_field)
id3 = '_{}_{}3'.format(db_table, primary_field)
queryset = super(NaturalOrderByManager, self).get_queryset().extra(select={
id1: "CAST(SUBSTRING({}.{} FROM '^(\d{{1,9}})') AS integer)".format(db_table, primary_field),
id2: "SUBSTRING({}.{} FROM '^\d*(.*?)\d*$')".format(db_table, primary_field),
id3: "CAST(SUBSTRING({}.{} FROM '(\d{{1,9}})$') AS integer)".format(db_table, primary_field),
})
ordering = fields[0:-1] + (id1, id2, id3)
return queryset.order_by(*ordering)