#303: First stab at implementing a natural ordering for sites, racks, and devices

netbox/utilities/managers.py

@@ -0,0 +1,30 @@
+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+)') AS integer)".format(db_table, primary_field),
+            id2: "SUBSTRING({}.{} FROM '^\d*(.*?)\d*$')".format(db_table, primary_field),
+            id3: "CAST(SUBSTRING({}.{} FROM '(\d+)$') AS integer)".format(db_table, primary_field),
+        })
+        ordering = fields[0:-1] + (id1, id2, id3)
+
+        return queryset.order_by(*ordering)