#13343: Wrong behavior of ManyToMany relationship while using 'trough' in
ManyToManyField and 'db_column' and 'to_field' properties in intermediate
model
---------------------------------------------------+------------------------
Reporter: twil | Owner: nobody
Status: new | Milestone: 1.2
Component: Database layer (models, ORM) | Version: 1.2-beta
Resolution: | Keywords:
Stage: Accepted | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by twil):
New, stripped down and abstract version of models:
{{{
#!python
from django.db import models
class Item(models.Model):
unique_field = models.IntegerField(unique = True)
title = models.CharField(max_length = 10)
class Group(models.Model):
title = models.CharField(max_length = 10)
members = models.ManyToManyField('Item', through = 'GroupItem')
class GroupItem(models.Model):
item = models.ForeignKey('Item', to_field = 'unique_field')
group = models.ForeignKey('Group')
title = models.CharField(max_length = 10)
}}}
and shell test sequence of commands:
{{{
#!text
Python 2.5.2 (r252:60911, Jan 4 2009, 17:40:26)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from testm2m.m2m.models import *
>>> item1 = Item.objects.create(unique_field = 100, title = 'Item')
>>> group1 = Group.objects.create(title = 'Group')
>>> membership = GroupItem.objects.create(item = item1, group = group1,
title = 'Membership')
>>> membership.save()
>>> group1.members.all()
[]
>>> from django.db import connection
>>> connection.queries
[{'time': '0.002', 'sql': u'INSERT INTO "m2m_item" ("unique_field",
"title") VALUES (100, Item)'}, {'time': '0.001', 'sql': u'INSERT INTO
"m2m_group" ("title") VALUES (Group)'}, {'time': '0.001', 'sql': u'INSERT
INTO "m2m_groupitem" ("item_id", "group_id", "title") VALUES (100, 1,
Membership)'}, {'time': '0.000', 'sql': u'SELECT (1) AS "a",
"m2m_groupitem"."id", "m2m_groupitem"."item_id",
"m2m_groupitem"."group_id", "m2m_groupitem"."title" FROM "m2m_groupitem"
WHERE "m2m_groupitem"."id" = 1 LIMIT 1'}, {'time': '0.001', 'sql':
u'UPDATE "m2m_groupitem" SET "item_id" = 100, "group_id" = 1, "title" =
Membership WHERE "m2m_groupitem"."id" = 1 '}, {'time': '0.000', 'sql':
u'SELECT "m2m_item"."id", "m2m_item"."unique_field", "m2m_item"."title"
FROM "m2m_item" INNER JOIN "m2m_groupitem" ON ("m2m_item"."id" =
"m2m_groupitem"."item_id") WHERE "m2m_groupitem"."group_id" = 1 LIMIT
21'}]
}}}
PS: I've tried to make patch but couldn't find right place in django code
:( I'll try tomorrow again.
--
Ticket URL: <http://code.djangoproject.com/ticket/13343#comment:2>
Django <http://code.djangoproject.com/>
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