Avoid project field collision.

Author: WaVEV

django_mongodb/compiler.py

@@ -5,7 +5,6 @@
 from django.db.models.expressions import Col, OrderBy, Value
 from django.db.models.sql import compiler
 from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE, MULTI, ORDER_DIR, SINGLE
-
 from django.utils.functional import cached_property
 
 from .base import Cursor
@@ -464,7 +463,8 @@ def get_project_fields(self, columns=None, ordering=None):
                     fields[alias] = 1
 
             for column, _ in ordering or []:
-                if column not in fields:
+                foreign_table = column.split(".", 1)[0] if "." in column else None
+                if column not in fields and foreign_table not in fields:
                     fields[column] = 1
 
         return fields