Fixed an isnull=False filtering edge-case. Fixes #15316.

The bulk of this patch is due to some fine analysis from Aleksandra
Sendecka.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16656 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 14 insertions, 5 deletions

diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index fd2e7a6d9a..e5e11f472a 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -1105,7 +1105,10 @@ class Query(object):
 
         # Process the join list to see if we can remove any inner joins from
         # the far end (fewer tables in a query is better).
-        col, alias, join_list = self.trim_joins(target, join_list, last, trim)
+        nonnull_comparison = (lookup_type == 'isnull' and value is False)
+        col, alias, join_list = self.trim_joins(target, join_list, last, trim,
+                nonnull_comparison)
+
         if connector == OR:
             # Some joins may need to be promoted when adding a new filter to a
             # disjunction. We walk the list of new joins and where it diverges
@@ -1442,7 +1445,7 @@ class Query(object):
 
         return field, target, opts, joins, last, extra_filters
 
-    def trim_joins(self, target, join_list, last, trim):
+    def trim_joins(self, target, join_list, last, trim, nonnull_check=False):
         """
         Sometimes joins at the end of a multi-table sequence can be trimmed. If
         the final join is against the same column as we are comparing against,
@@ -1463,6 +1466,11 @@ class Query(object):
         trimmed before anything. See the documentation of add_filter() for
         details about this.
 
+        The 'nonnull_check' parameter is True when we are using inner joins
+        between tables explicitly to exclude NULL entries. In that case, the
+        tables shouldn't be trimmed, because the very action of joining to them
+        alters the result set.
+
         Returns the final active column and table alias and the new active
         join_list.
         """
@@ -1470,7 +1478,7 @@ class Query(object):
         penultimate = last.pop()
         if penultimate == final:
             penultimate = last.pop()
-        if trim and len(join_list) > 1:
+        if trim and final > 1:
             extra = join_list[penultimate:]
             join_list = join_list[:penultimate]
             final = penultimate
@@ -1483,12 +1491,13 @@ class Query(object):
         alias = join_list[-1]
         while final > 1:
             join = self.alias_map[alias]
-            if col != join[RHS_JOIN_COL] or join[JOIN_TYPE] != self.INNER:
+            if (col != join[RHS_JOIN_COL] or join[JOIN_TYPE] != self.INNER or
+                    nonnull_check):
                 break
             self.unref_alias(alias)
             alias = join[LHS_ALIAS]
             col = join[LHS_JOIN_COL]
-            join_list = join_list[:-1]
+            join_list.pop()
             final -= 1
             if final == penultimate:
                 penultimate = last.pop()