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Fixed deferred fields and select_related() interaction.

Loading related models when some fields were deferred was resulting in
incorrect offsets being used into the results row, causing the wrong data to be
assigned to attributes.

Refs #10710. This fixes the first of two bugs reported there.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10383 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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commit 0a89a57ffc491f2d1ff9a19e792739f67a945be3 1 parent dded5f5
Malcolm Tredinnick malcolmt authored
49 django/db/models/query.py
View
@@ -908,31 +908,35 @@ def get_cached_row(klass, row, index_start, max_depth=0, cur_depth=0,
return None
restricted = requested is not None
- index_end = index_start + len(klass._meta.fields)
- fields = row[index_start:index_end]
- if not [x for x in fields if x is not None]:
- # If we only have a list of Nones, there was not related object.
- obj = None
- else:
- load_fields = only_load and only_load.get(klass) or None
- if load_fields:
- # Handle deferred fields.
- skip = set()
- init_list = []
- pk_val = fields[klass._meta.pk_index()]
- for field in klass._meta.fields:
- if field.name not in load_fields:
- skip.add(field.name)
- else:
- init_list.append(field.attname)
- if skip:
- klass = deferred_class_factory(klass, skip)
- obj = klass(**dict(zip(init_list, fields)))
+ load_fields = only_load and only_load.get(klass) or None
+ if load_fields:
+ # Handle deferred fields.
+ skip = set()
+ init_list = []
+ pk_val = row[index_start + klass._meta.pk_index()]
+ for field in klass._meta.fields:
+ if field.name not in load_fields:
+ skip.add(field.name)
else:
- obj = klass(*fields)
+ init_list.append(field.attname)
+ field_count = len(init_list)
+ fields = row[index_start : index_start + field_count]
+ if fields == (None,) * field_count:
+ obj = None
+ elif skip:
+ klass = deferred_class_factory(klass, skip)
+ obj = klass(**dict(zip(init_list, fields)))
else:
obj = klass(*fields)
- index_end += offset
+ else:
+ field_count = len(klass._meta.fields)
+ fields = row[index_start : index_start + field_count]
+ if fields == (None,) * field_count:
+ obj = None
+ else:
+ obj = klass(*fields)
+
+ index_end = index_start + field_count + offset
for f in klass._meta.fields:
if not select_related_descend(f, restricted, requested):
continue
@@ -948,7 +952,6 @@ def get_cached_row(klass, row, index_start, max_depth=0, cur_depth=0,
setattr(obj, f.get_cache_name(), rel_obj)
return obj, index_end
-
def delete_objects(seen_objs):
"""
Iterate through a list of seen classes, and remove any instances that are
20 tests/regressiontests/defer_regress/models.py
View
@@ -17,6 +17,18 @@ def __unicode__(self):
class RelatedItem(models.Model):
item = models.ForeignKey(Item)
+class Child(models.Model):
+ name = models.CharField(max_length=10)
+ value = models.IntegerField()
+
+class Leaf(models.Model):
+ name = models.CharField(max_length=10)
+ child = models.ForeignKey(Child)
+ value = models.IntegerField(default=42)
+
+ def __unicode__(self):
+ return self.name
+
__test__ = {"regression_tests": """
Deferred fields should really be deferred and not accidentally use the field's
default value just because they aren't passed to __init__.
@@ -66,7 +78,15 @@ class RelatedItem(models.Model):
>>> r.item == i
True
+Some further checks for select_related() and inherited model behaviour
+(regression for #10710).
+
+>>> c1 = Child.objects.create(name="c1", value=42)
+>>> obj = Leaf.objects.create(name="l1", child=c1)
+>>> obj = Leaf.objects.only("name", "child").select_related()[0]
+>>> obj.child.name
+u'c1'
"""
}
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