raise NotSupportedError for QuerySet.prefetch_related()

Author: timgraham

README.md

@@ -114,6 +114,7 @@ Migrations for 'admin':
   - `datetimes()`
   - `distinct()`
   - `extra()`
+  - `prefetch_related()`
 
 - `Subquery`, `Exists`, and using a `QuerySet` in `QuerySet.annotate()` aren't
   supported.

django_mongodb/compiler.py

@@ -101,6 +101,8 @@ def check_query(self):
                 raise NotSupportedError("QuerySet.dates() is not supported on MongoDB.")
             raise NotSupportedError("QuerySet.distinct() is not supported on MongoDB.")
         if self.query.extra:
+            if any(key.startswith("_prefetch_related_") for key in self.query.extra):
+                raise NotSupportedError("QuerySet.prefetch_related() is not supported on MongoDB.")
             raise NotSupportedError("QuerySet.extra() is not supported on MongoDB.")
         if any(
             isinstance(a, Aggregate) and not isinstance(a, Count)