Ticket #3050: values.diff

django/db/models/query.py

@@ -510 +510 @@
 
 class ValuesQuerySet(QuerySet):
     def iterator(self):
-        # select_related and select aren't supported in values().
+        # select_related isn't supported in values().
         self._select_related = False
-        self._select = {}
 
         # self._fields is a list of field names to fetch.
         if self._fields:
-            columns = [self.model._meta.get_field(f, many_to_many=False).column for f in self._fields]
+            if not self._select:
+                columns = [self.model._meta.get_field(f, many_to_many=False).column for f in self._fields]
+            else:
+                columns = []
+                for f in self._fields:
+                    if f in [field.name for field in self.model._meta.fields]:
+                        columns.append( self.model._meta.get_field(f, many_to_many=False).column )
+                    elif not self._select.has_key( f ):
+                        raise FieldDoesNotExist, '%s has no field named %r' % ( self.model._meta.object_name, f )
+
+
             field_names = self._fields
         else: # Default to all fields.
             columns = [f.column for f in self.model._meta.fields]
@@ -525 +534 @@
         cursor = connection.cursor()
         select, sql, params = self._get_sql_clause()
         select = ['%s.%s' % (backend.quote_name(self.model._meta.db_table), backend.quote_name(c)) for c in columns]
+
+        # Add any additional SELECTs.
+        if self._select:
+            select.extend(['(%s) AS %s' % (quote_only_if_word(s[1]), backend.quote_name(s[0])) for s in self._select.items()])
+        
         cursor.execute("SELECT " + (self._distinct and "DISTINCT " or "") + ",".join(select) + sql, params)
         while 1:
             rows = cursor.fetchmany(GET_ITERATOR_CHUNK_SIZE)

tests/modeltests/lookup/models.py

@@ -106 +106 @@
 [('headline', 'Article 7'), ('id', 7)]
 [('headline', 'Article 1'), ('id', 1)]
 
+# you can use values() even on extra fields
+>>> for d in Article.objects.extra( select={'id_plus_one' : 'id + 1'} ).values('id', 'id_plus_one'):
+...     i = d.items()
+...     i.sort()
+...     i
+[('id', 5), ('id_plus_one', 6)]
+[('id', 6), ('id_plus_one', 7)]
+[('id', 4), ('id_plus_one', 5)]
+[('id', 2), ('id_plus_one', 3)]
+[('id', 3), ('id_plus_one', 4)]
+[('id', 7), ('id_plus_one', 8)]
+[('id', 1), ('id_plus_one', 2)]
+
+# however, an exception FieldDoesNotExist will still be thrown 
+# if you try to access non-existent field (field that is neither in model nor extra)
+>>> Article.objects.extra( select={'id_plus_one' : 'id + 1'} ).values('id', 'id_plus_two')
+Traceback (most recent call last):
+    ...
+FieldDoesNotExist: Article has no field named 'id_plus_two'
+
 # You can use values() with iterator() for memory savings, because iterator()
 # uses database-level iteration.
 >>> for d in Article.objects.values('id', 'headline').iterator():