Fixes #531: Order prefixes by VRF assignment

netbox/utilities/sql.py

@@ -0,0 +1,32 @@
+from django.db import connections, models
+from django.db.models.sql.compiler import SQLCompiler
+
+
+class NullsFirstSQLCompiler(SQLCompiler):
+
+    def get_order_by(self):
+        result = super(NullsFirstSQLCompiler, self).get_order_by()
+        if result:
+            return [(expr, (sql + ' NULLS FIRST', params, is_ref)) for (expr, (sql, params, is_ref)) in result]
+        return result
+
+
+class NullsFirstQuery(models.sql.query.Query):
+
+    def get_compiler(self, using=None, connection=None):
+        if using is None and connection is None:
+            raise ValueError("Need either using or connection")
+        if using:
+            connection = connections[using]
+        return NullsFirstSQLCompiler(self, connection, using)
+
+
+class NullsFirstQuerySet(models.QuerySet):
+    """
+    Override PostgreSQL's default behavior of ordering NULLs last. This is needed e.g. to order Prefixes in the global
+    table before those assigned to a VRF.
+    """
+
+    def __init__(self, model=None, query=None, using=None, hints=None):
+        super(NullsFirstQuerySet, self).__init__(model, query, using, hints)
+        self.query = query or NullsFirstQuery(self.model)