Fixed #2473 -- Added special case for '__in=[]' (empty set) queries, because 'WHERE attr IN ()' is invalid SQL on many backends. Thanks, Gary Wilson.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@4283 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 9 insertions, 1 deletions

diff --git a/django/db/models/query.py b/django/db/models/query.py
index 53ed63ae5b..f42e8cfd42 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -641,7 +641,15 @@ def get_where_clause(lookup_type, table_prefix, field_name, value):
     except KeyError:
         pass
     if lookup_type == 'in':
-        return '%s%s IN (%s)' % (table_prefix, field_name, ','.join(['%s' for v in value]))
+        in_string = ','.join(['%s' for id in value])
+        if in_string:
+            return '%s%s IN (%s)' % (table_prefix, field_name, in_string)
+        else:
+            # Most backends do not accept an empty string inside the IN
+            # expression, i.e. cannot do "WHERE ... IN ()".  Since there are
+            # also some backends that do not accept "WHERE false", we instead
+            # use an expression that always evaluates to False.
+            return '0=1'
     elif lookup_type == 'range':
         return '%s%s BETWEEN %%s AND %%s' % (table_prefix, field_name)
     elif lookup_type in ('year', 'month', 'day'):