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Fixed #17485 -- Made defer work with select_related

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This commit tackles a couple of issues. First, in certain cases there
were some mixups if field.attname or field.name should be deferred.
Field.attname is now always used.

Another issue tackled is a case where field is both deferred by
.only(), and selected by select_related. This case is now an error.

A lot of thanks to koniiiik (Michal Petrucha) for the patch, and
to Andrei Antoukh for review.
This commit is contained in:
Anssi Kääriäinen 2012-06-26 18:08:42 +03:00
parent 5318783027
commit b6c356b7bb
9 changed files with 81 additions and 21 deletions
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13
django/db/models/query_utils.py
View file

@ -126,18 +126,19 @@ class DeferredAttribute(object):
return None
def select_related_descend(field, restricted, requested, reverse=False):
def select_related_descend(field, restricted, requested, load_fields, reverse=False):
"""
Returns True if this field should be used to descend deeper for
select_related() purposes. Used by both the query construction code
(sql.query.fill_related_selections()) and the model instance creation code
(query.get_cached_row()).
(query.get_klass_info()).
Arguments:
* field - the field to be checked
* restricted - a boolean field, indicating if the field list has been
manually restricted using a requested clause)
* requested - The select_related() dictionary.
* load_fields - the set of fields to be loaded on this model
* reverse - boolean, True if we are checking a reverse select related
"""
if not field.rel:
@ -151,6 +152,14 @@ def select_related_descend(field, restricted, requested, reverse=False):
return False
if not restricted and field.null:
return False
if load_fields:
if field.name not in load_fields:
if restricted and field.name in requested:
raise InvalidQuery("Field %s.%s cannot be both deferred"
" and traversed using select_related"
" at the same time." %
(field.model._meta.object_name, field.name))
return False
return True
# This function is needed because data descriptors must be defined on a class