Fixed #11670 -- Prevented genuine model fields named 'year', 'month', 'gt', 'lt' etc. from being mistaken for lookup types in lookups across relations. Thanks to andy for the report, to jpwatts for the initial patch and to Anssi Kääriäinen and Alex Gaynor for the reviews.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17450 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -1061,11 +1061,31 @@ class Query(object):
         if not parts:
             raise FieldError("Cannot parse keyword query %r" % arg)
 
-        # Work out the lookup type and remove it from 'parts', if necessary.
-        if len(parts) == 1 or parts[-1] not in self.query_terms:
-            lookup_type = 'exact'
-        else:
-            lookup_type = parts.pop()
+        # Work out the lookup type and remove it from the end of 'parts',
+        # if necessary.
+        lookup_type = 'exact' # Default lookup type
+        num_parts = len(parts)
+        if (len(parts) > 1 and parts[-1] in self.query_terms
+            and arg not in self.aggregates):
+            # Traverse the lookup query to distinguish related fields from
+            # lookup types.
+            lookup_model = self.model
+            for counter, field_name in enumerate(parts):
+                try:
+                    lookup_field = lookup_model._meta.get_field(field_name)
+                except FieldDoesNotExist:
+                    # Not a field. Bail out.
+                    lookup_type = parts.pop()
+                    break
+                # Unless we're at the end of the list of lookups, let's attempt
+                # to continue traversing relations.
+                if (counter + 1) < num_parts:
+                    try:
+                        lookup_model = lookup_field.rel.to
+                    except AttributeError:
+                        # Not a related field. Bail out.
+                        lookup_type = parts.pop()
+                        break
 
         # By default, this is a WHERE clause. If an aggregate is referenced
         # in the value, the filter will be promoted to a HAVING