#12328: subqueries in django 1.1 behave oddly
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Reporter: wdoekes | Owner:
marcosmoyano
Status: assigned | Milestone: 1.2
Component: Database layer (models, ORM) | Version: 1.1
Resolution: | Keywords:
Stage: Accepted | Has_patch: 1
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by marcosmoyano):
There's still an issue in the delete() method. Although modifying the
while statemente solves the issue, this solution requires and extra query,
which is not the desired solution.
Here's a closer look at the problem.
{{{
In [1]: from ticket_12328.models import *
In [2]: M.objects.create(id=1)
Out[2]: <M: M(id=1)>
In [3]: M.objects.create(id=2)
Out[3]: <M: M(id=2)>
In [4]: M.objects.create(id=3)
Out[4]: <M: M(id=3)>
In [5]: M.objects.all()
Out[5]: [<M: M(id=1)>, <M: M(id=2)>, <M: M(id=3)>]
In [6]: M.objects.filter(id__in=M.objects.order_by('id')[:1]).delete()
> /usr/lib/python2.6/site-packages/django/db/models/query.py(433)delete()
432 import ipdb;ipdb.set_trace()
--> 433 while 1:
434 #for element in xrange(del_query.count()):
ipdb> print del_query.query
SELECT "ticket_12328_m"."id" FROM "ticket_12328_m" WHERE
"ticket_12328_m"."id" IN (SELECT U0."id" FROM "ticket_12328_m" U0 ORDER BY
U0."id" ASC LIMIT 1)
ipdb> n
> /usr/lib/python2.6/site-packages/django/db/models/query.py(437)delete()
436 # objects that are related to the objects that are to
be deleted.
--> 437 seen_objs = CollectedObjects(seen_objs)
438 for object in del_query[:CHUNK_SIZE]:
}}}
On line #438 every time del_query gets evaluated it will return the first
element from the table (ordered by id) until there are no more elements to
consume.
--
Ticket URL: <http://code.djangoproject.com/ticket/12328#comment:8>
Django <http://code.djangoproject.com/>
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