Moved querysets to separate files; tweaked interface ordering logic (#1523)

netbox/ipam/querysets.py

@@ -0,0 +1,38 @@
+from __future__ import unicode_literals
+
+from utilities.sql import NullsFirstQuerySet
+
+
+class PrefixQuerySet(NullsFirstQuerySet):
+
+    def annotate_depth(self, limit=None):
+        """
+        Iterate through a QuerySet of Prefixes and annotate the hierarchical level of each. While it would be preferable
+        to do this using .extra() on the QuerySet to count the unique parents of each prefix, that approach introduces
+        performance issues at scale.
+
+        Because we're adding a non-field attribute to the model, annotation must be made *after* any QuerySet
+        modifications.
+        """
+        queryset = self
+        stack = []
+        for p in queryset:
+            try:
+                prev_p = stack[-1]
+            except IndexError:
+                prev_p = None
+            if prev_p is not None:
+                while (p.prefix not in prev_p.prefix) or p.prefix == prev_p.prefix:
+                    stack.pop()
+                    try:
+                        prev_p = stack[-1]
+                    except IndexError:
+                        prev_p = None
+                        break
+            if prev_p is not None:
+                prev_p.has_children = True
+            stack.append(p)
+            p.depth = len(stack) - 1
+        if limit is None:
+            return queryset
+        return list(filter(lambda p: p.depth <= limit, queryset))