[Django] #19607: prefetch

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Jan 14, 2013, 10:13:25 AM1/14/13

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#19607: prefetch_related bug
----------------------------------------------+----------------------
Reporter: av@… | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: 1.4
Severity: Release blocker | Keywords: prefetch
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------------------------+----------------------
In file django/db/models/query.py line 1613, else statement sould not
breaks an iteration, because in some queries obj_list is like [obj1, obj2,
obj3] where obj2 has _prefetched_objects_cache, but obj3 has not.

So later in prefetch_one_level() we have "object has no attribute
'_prefetched_objects_cache'" error.

Code:
for obj in obj_list:
if not hasattr(obj, '_prefetched_objects_cache'):
try:
obj._prefetched_objects_cache = {}
except AttributeError:
# Must be in a QuerySet subclass that is not
returning
# Model instances, either in Django or 3rd
# party. prefetch_related() doesn't make sense, so
quit
# now.
good_objects = False
break
else:
# We already did this list
break <------ Line 1613 -------------- this one
sould be changed to pass

--
Ticket URL: <https://code.djangoproject.com/ticket/19607>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

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Jan 14, 2013, 12:39:06 PM1/14/13

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Easy pickings: 0 | UI/UX: 0

-------------------------------------+-------------------------------------
Changes (by ptone):

* status: new => closed
* severity: Release blocker => Normal
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
* resolution: => needsinfo

Old description:

> In file django/db/models/query.py line 1613, else statement sould not
> breaks an iteration, because in some queries obj_list is like [obj1,
> obj2, obj3] where obj2 has _prefetched_objects_cache, but obj3 has not.
>
> So later in prefetch_one_level() we have "object has no attribute
> '_prefetched_objects_cache'" error.
>
> Code:
> for obj in obj_list:
> if not hasattr(obj, '_prefetched_objects_cache'):
> try:
> obj._prefetched_objects_cache = {}
> except AttributeError:
> # Must be in a QuerySet subclass that is not
> returning
> # Model instances, either in Django or 3rd
> # party. prefetch_related() doesn't make sense,
> so quit
> # now.
> good_objects = False
> break
> else:
> # We already did this list
> break <------ Line 1613 -------------- this one
> sould be changed to pass

New description:

In file django/db/models/query.py line 1613, else statement sould not
breaks an iteration, because in some queries obj_list is like [obj1, obj2,
obj3] where obj2 has _prefetched_objects_cache, but obj3 has not.

So later in prefetch_one_level() we have "object has no attribute
'_prefetched_objects_cache'" error.

Code:
{{{
for obj in obj_list:
if not hasattr(obj, '_prefetched_objects_cache'):
try:
obj._prefetched_objects_cache = {}
except AttributeError:
# Must be in a QuerySet subclass that is not
returning
# Model instances, either in Django or 3rd
# party. prefetch_related() doesn't make sense, so
quit
# now.
good_objects = False
break
else:
# We already did this list
break <------ Line 1613 -------------- this one
sould be changed to pass
}}}

--

Comment:

From a cursory look - the code for this has not changed between 1.4 and
1.5 - so is unlikely to be a regression, and so not a blocker for 1.5

I haven't yet tried to verify the bug - can you provide more detail on how
to recreate the problem query, even better is to provide it in the form of
a failing test case.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:1>

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Feb 24, 2013, 11:14:06 AM2/24/13

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#19607: prefetch_related bug
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody

Needs tests: 0 | Patch needs improvement: 0

Easy pickings: 0 | UI/UX: 0

-------------------------------------+-------------------------------------

Comment (by smyrman):

We have had several errors for this on http://dusken.no while using
prefetch related. We have had several bug reports regarding this. The
issues is hard to reproduce, but seems most likely to occur after objects
have recently been changed in the database (for our case, after someone
publishes another video).

On one specific view (http://dusken.no/tv/siste/) We have about 17-18 hits
for this error in a period of two months. The daily traffic would be
between 100 and 500 visitors for this view, and there are currently no
applied HTML caching.

Here is the code we suspect. There are several:

{{{
feature_episodes =
Episode.objects.filter(is_published=True).order_by('-priority').select_related('season',
'image').prefetch_related('category', 'season__series',
'season__series__category')[:5]

}}}

And also:
{{{
if category == 'siste':
episodes =
Episode.objects.filter(is_published=True).order_by('-priority',
'-public_from').select_related('season',
'image').prefetch_related('category', 'season__series__category')
{{{

Her is the stack trace:

{{{
Traceback (most recent call last):

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/core/handlers/base.py", line 111, in get_response
response = callback(request, *callback_args, **callback_kwargs)

File "/srv/www/www.dusken.no/src/video/series/views.py", line 84, in
list
'feature_episodes': feature_episodes,

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/shortcuts/__init__.py", line 44, in render
return HttpResponse(loader.render_to_string(*args, **kwargs),

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/loader.py", line 176, in render_to_string
return t.render(context_instance)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/base.py", line 140, in render
return self._render(context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/base.py", line 134, in _render
return self.nodelist.render(context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/base.py", line 823, in render
bit = self.render_node(node, context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/debug.py", line 74, in render_node
return node.render(context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/loader_tags.py", line 123, in render
return compiled_parent._render(context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/base.py", line 134, in _render
return self.nodelist.render(context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/base.py", line 823, in render
bit = self.render_node(node, context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/debug.py", line 74, in render_node
return node.render(context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/loader_tags.py", line 62, in render
result = block.nodelist.render(context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/base.py", line 823, in render
bit = self.render_node(node, context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/debug.py", line 74, in render_node
return node.render(context)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/template/defaulttags.py", line 145, in render
len_values = len(values)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/db/models/query.py", line 89, in __len__
self._prefetch_related_objects()

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/db/models/query.py", line 570, in
_prefetch_related_objects
prefetch_related_objects(self._result_cache,
self._prefetch_related_lookups)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/db/models/query.py", line 1680, in
prefetch_related_objects
obj_list, additional_prl = prefetch_one_level(obj_list, prefetcher,
attr)

File "/srv/www/www.dusken.no/DUSKEN/lib/python2.6/site-
packages/django/db/models/query.py", line 1808, in prefetch_one_level
obj._prefetched_objects_cache[cache_name] = qs

AttributeError: 'Series' object has no attribute
'_prefetched_objects_cache'
}}}

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:2>

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Mar 28, 2013, 5:05:22 AM3/28/13

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#19607: prefetch_related bug
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Component: Database layer | Version: 1.4
(models, ORM) | Resolution:

Severity: Normal | Triage Stage:
Keywords: prefetch | Unreviewed

Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0

Easy pickings: 0 | UI/UX: 0

-------------------------------------+-------------------------------------
Changes (by xyzman):

* status: closed => new
* has_patch: 0 => 1
* resolution: needsinfo =>

Comment:

The issue is hard to reproduce, but it seems to occur more when queryset
has nested relations with more than one related object in "child" data
set.

Anyway, proposed patch fixes the issue completely, and from quick review
it looks like there was either a typo or logical mistake. Anyway, fixing
it here seems better than spending hours on trying to reproduce it.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:3>

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Mar 28, 2013, 7:09:17 AM3/28/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Component: Database layer | Version: 1.4
(models, ORM) | Resolution:
Severity: Normal | Triage Stage:
Keywords: prefetch | Unreviewed

prefetch_related | Needs documentation: 0
Has patch: 1 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
-------------------------------------+-------------------------------------
Changes (by tonnzor):

* keywords: prefetch => prefetch prefetch_related

Comment:

I face the same issue on big data set.

It is crashing every time, so it should be fixed ASAP.

There's an obvious workaround (do not use prefetch_related), but in some
of my cases it gives 10x performance drop, so it is no longer an option.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:4>

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Mar 28, 2013, 7:31:06 AM3/28/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by tonnzor):

Did a clone with patch applied
https://github.com/tonnzor/django/commit/f72483bce99de70380c0ef610f87905cc7812a1d
Also passed pull request https://github.com/django/django/pull/970

Please review and apply them

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:5>

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Mar 28, 2013, 7:36:28 AM3/28/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by mjtamlyn):

We can't merge this without a test case. The original logic looks sound
enough to me, and in any case the correct fix would not be to replace it
with a `pass`, rather remove the `else` clause all together.

The logic we would be removing is a slight logical optimisation for
performance so I don't think applying this fix would break anything, but
we should still find out why it's broken as it is.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:6>

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Mar 28, 2013, 7:37:05 AM3/28/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Changes (by mjtamlyn):

* cc: marc.tamlyn@… (added)

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:7>

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Mar 28, 2013, 2:52:01 PM3/28/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by lukeplant):

From what I can tell, you are hitting on a case we are deliberately not
supporting - a lookup that returns heterogeneous set of objects. At each
stage of traversing the prefetch_related chain, the set of objects that
are retrieved must be a homogeneous set of objects. If it is not, then you
cannot reliably do the next step - the logic that collects the primary key
values and does the next lookup assumes you can do the lookup on the same
table.

So I deliberately put 'break' there. Also, it is a necessary optimisation
to avoid duplicate work in some genuinely possible situations.

Of course, it is possible there is a bug in the logic, and a case I didn't
consider, but we need a reproducible test case before we change anything.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:8>

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Mar 29, 2013, 2:39:24 PM3/29/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by av@…):

lukeplant, im submitter

i kill a day to reproduce bug, but it f..'n difficult :)

As i understood, the bug happens, when model has 'self' referenced foreign
key, and prefetched that key's related_name set

for example:

{{{
class Document(models.Model):
folder = models.ForeignKey(Folder)
from_persons = models.ManyToManyField(Person,
related_name='documents_from', blank=True, null=True)
to_persons = models.ManyToManyField(Person,
related_name='documents_to', blank=True, null=True)
doc_request = models.ForeignKey('self', related_name='answers',
blank=True, null=True)

Document.objects.all().select_related('doc_request').prefetch_related('answers',
'answers__from_persons', 'answers__to_persons')

}}}

and bug occurs in a second iteration of prefetch, when 'answers', that are
Document instances too, trying to cache {{{ answers__folder }}} instances,
such Folder instance hasn't _prefetched_objects_cache
and this is so difficult intersection of 'self' tree, that it will taked a
time to check it out.

Next week i'll checked out this 'buggy' object from production database
with all relations and try to reproduce bug with failed test.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:9>

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Mar 29, 2013, 5:59:12 PM3/29/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by lukeplant):

Thanks so much for taking the time to do that av - I realise these things
take a long time to debug, and it can seem like we are looking for excuses
not to do work, but past experience tells us that we really have to
understand the bug before fixing. Thanks for persevering, I'll wait for
your test case.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:10>

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Apr 26, 2013, 7:04:57 PM4/26/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by morgan@…):

I can reliably reproduce this error (although I don't know if it's this
bug).

Given

{{{
class Task(Model):
category = ForeignKey('Category')
for_ct = ForeignKey(ContentType)
for_pk = PositiveIntegerField()
for = GenericForeignKey(
content_type_field='for_ct',
object_id_field='for_pk',
)

class Thingy(Model):
tasks = generic.GenericRelation(Task)
}}}

I'd like to do

{{{ Task.objects.prefetch_related('for__tasks__category')}}}

But I get the error: {{{ 'Thingy' object has no attribute
'_prefetched_objects_cache'}}}

{{{ Task.objects.prefetch_related('for__fk_field_on_thingy')}}} works just
fine, as does {{{ Thingy.objects.prefetch_related('tasks')}}}

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:11>

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Apr 29, 2013, 11:23:27 AM4/29/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by lukeplant):

Replying to [comment:11 morgan@…]:

> I can reliably reproduce this error (although I don't know if it's this
bug).

If you could create a patch with a failing test, that would be a huge
help. You need to be able to run the Django test suite, and add your
models to tests/prefetch_related/models.py and the tests to
tests/prefect_related/tests.py. You can create a new test class if that's
easiest e.g. `Ticket19607Tests`

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:12>

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May 19, 2013, 10:12:19 AM5/19/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by nmundar):

I've just spent couple of hours trying to create the tests for this case
and I've gone through the model examples in this discussion but I wasn't
able to reproduce it so if anyone is interested in the issue here are
Morgans models (he claims he could reproduce the issue reliably) that
should go into '''tests/prefetch_related/models.py'''. I've replaced
Cathegory FK with Author FK because that is the model that is already
available in tests.

{{{

class Task(models.Model):
author = models.ForeignKey('Author')
content_type = models.ForeignKey(ContentType)
object_id = models.PositiveIntegerField()
content_object = generic.GenericForeignKey('content_type',
'object_id')

class Thingy(models.Model):
tasks = generic.GenericRelation(Task)

}}}

You can setup '''tests/prefetch_related/tests.py''' like this:

{{{
from .models import (... Task, Thingy)

class PrefetchRelatedTests(TestCase):

def setUp(self):

# ...

self.thingy1 = Thingy.objects.create()
self.task1 = Task.objects.create(author=self.author1,
content_object=self.thingy1)

self.thingy2 = Thingy.objects.create()
self.task2 = Task.objects.create(author=self.author2,
content_object=self.thingy2)

def test_ticket_19607_bug(self):
t = Task.objects.prefetch_related('content_object__tasks__author')

}}}

so now you can play around with Thingy/Task models and try to reproduce
the bug. You can run a single test with:

{{{./runtests.py --settings=test_sqlite
prefetch_related.tests.PrefetchRelatedTests.test_ticket_19607_bug}}}

so maybe this can help if there is somebody who can reproduce the issue,
but doesn't know where to start with tests.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:13>

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May 21, 2013, 3:50:47 PM5/21/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by kenn.knowles@…):

I have a completely mundane project where I actually have work very hard
*not* to trigger this error. It manifests quickly when setting up an admin
UI, where lots of ModelAdmin classes need to share each others'
prefetch_related lookups.

I do not really have time to isolate a test case now, but a big +1 for
this fix. A performance hit is vastly preferable to being unable to use
the feature.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:14>

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May 22, 2013, 5:45:44 AM5/22/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by lukeplant):

Thanks kenn - but I'm afraid this is really going nowhere without some
understanding of the issue, and if no-one isolates a test case, then we
probably will not understand the issue. There is no question that we want
to fix it, so an additional +1 tells us nothing.

I'm not trying to be rude, but lots of people saying "Please fix this, but
I don't have time to help", doesn't actually help us, it only takes up
time reading messages.

If someone comes up with a test case, I'm happy to pledge the time needed
to fix it. But I've never seen the error myself.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:15>

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May 23, 2013, 2:03:06 PM5/23/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by kenn.knowles@…):

I mean the +1 to add a vote to the severity of the issue, nothing more.

And you are in luck. My admin cannot be performant without fixing this,
and there is not apparently any workaround, so I am working on isolating
the failure by replicating my project and removing pieces until it is
suitable for public upload. Unfortunately a direct replica with a few
hand-entered models has not caused the error.

Perhaps you can clarify this statement, which might be a clue:

"From what I can tell, you are hitting on a case we are deliberately not
supporting - a lookup that returns heterogeneous set of objects. At each
stage of traversing the prefetch_related chain, the set of objects that
are retrieved must be a homogeneous set of objects."

My case is probably not that complex, so I doubt it applies

{{{
class Person(Model):
...

class Relation1(Model):
person1 = ForeignKey(Person, related_name='relation1_as_person1')
person2 = ForeignKey(Person, related_name='relation1_as_person2')

class Relation2(Model):
person1 = ForeignKey(Person, related_name='relation2_as_person1')
person2 = ForeignKey(Person, related_name='relation2_as_person2')
relation1 = ForeignKey(Relation1)
}}}

And this always crashes, but apparently requires some involved data to
trigger:

{{{
Relation2.objects.prefetch_related(
'person1',
'person2',
'relation1',
'relation1__person1',
'relation1__person2',
'person1__relation1_as_person1',
'person2__relation1_as_person2'
)
}}}

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:16>

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May 23, 2013, 2:54:42 PM5/23/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by lukeplant):

If you could post some example data that triggers it, that would be
awesome. Thanks!

From the look of your models, it doesn't sound like my suspicion above was
correct, since that could only apply if you were using
`GenericForeignKey`.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:17>

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May 23, 2013, 6:56:30 PM5/23/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by flarno11@…):

For me it happens with these models:

{{{
from django.db import models

class Lesson(models.Model):
name = models.CharField(max_length=200)

def __unicode__(self):
return self.name

class LessonEntry(models.Model):
lesson = models.ForeignKey(Lesson)

def __unicode__(self):
return self.lesson.__unicode__() + " - " + self.name1 + " - " +
self.name2

class WordEntry(models.Model):
lessonEntry = models.ForeignKey(LessonEntry)
name = models.CharField(max_length=200)

def __unicode__(self):
return self.name + ' (' + self.lang_id + ',' + str(self.id) + ')'
}}}

and this query:
{{{
>>> from zfvocapp.models import *
>>>
WordEntry.objects.filter(lessonEntry__lesson_id=57).prefetch_related('lessonEntry').prefetch_related('lessonEntry__wordentry_set')

Traceback (most recent call last):

File "<console>", line 1, in <module>
File "/Users/flo/Projects/zfvocapp/zfvocapp/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 77, in __repr__
data = list(self[:REPR_OUTPUT_SIZE + 1])
File "/Users/flo/Projects/zfvocapp/zfvocapp/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 102, in __iter__
len(self)
File "/Users/flo/Projects/zfvocapp/zfvocapp/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 94, in __len__
self._prefetch_related_objects()
File "/Users/flo/Projects/zfvocapp/zfvocapp/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 601, in
_prefetch_related_objects
prefetch_related_objects(self._result_cache,
self._prefetch_related_lookups)
File "/Users/flo/Projects/zfvocapp/zfvocapp/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 1746, in

prefetch_related_objects
obj_list, additional_prl = prefetch_one_level(obj_list, prefetcher,
attr)

File "/Users/flo/Projects/zfvocapp/zfvocapp/venv/lib/python2.7/site-
packages/django/db/models/query.py", line 1878, in prefetch_one_level
obj._prefetched_objects_cache[cache_name] = qs
AttributeError: 'LessonEntry' object has no attribute
'_prefetched_objects_cache'
}}}

but only when larger results are returned. and only with a postgresql
database and not with sqlite.

this is the relevant part of the data dump:
{{{
CREATE TABLE zfvocapp_lesson (
id integer NOT NULL,
"languagePair_id" integer NOT NULL,
name character varying(200) NOT NULL,
"createdAt" timestamp with time zone NOT NULL,
"modifiedAt" timestamp with time zone NOT NULL
);

CREATE TABLE zfvocapp_lessonentry (
id integer NOT NULL,
lesson_id integer NOT NULL,
name1 character varying(200) NOT NULL,
name2 character varying(200) NOT NULL,
"createdAt" timestamp with time zone NOT NULL,
"modifiedAt" timestamp with time zone NOT NULL
);

CREATE TABLE zfvocapp_wordentry (
id integer NOT NULL,
"lessonEntry_id" integer NOT NULL,
name character varying(200) NOT NULL,
lang_id character varying(2) NOT NULL,
"createdAt" timestamp with time zone NOT NULL,
"modifiedAt" timestamp with time zone NOT NULL
);

INSERT INTO zfvocapp_lesson VALUES (57, 2, 'Adjectives', '2013-05-22
20:57:05.105265+00', '2013-05-22 20:57:05.105292+00');

INSERT INTO zfvocapp_lessonentry VALUES (2163, 57, 'jung', 'young',
'2013-05-22 20:57:19.760508+00', '2013-05-22 20:57:19.800419+00');
INSERT INTO zfvocapp_lessonentry VALUES (2164, 57, 'schwarz', 'black',
'2013-05-22 21:10:43.795717+00', '2013-05-22 21:10:43.842123+00');
INSERT INTO zfvocapp_lessonentry VALUES (2172, 57, 'klein', 'small',
'2013-05-22 21:12:27.245094+00', '2013-05-22 21:12:27.281923+00');
INSERT INTO zfvocapp_lessonentry VALUES (2165, 57, 'weiss', 'white',
'2013-05-22 21:10:47.624582+00', '2013-05-22 21:10:47.652554+00');
INSERT INTO zfvocapp_lessonentry VALUES (2176, 57, 'glücklich', 'happy',
'2013-05-22 21:13:50.657134+00', '2013-05-22 21:13:50.686634+00');
INSERT INTO zfvocapp_lessonentry VALUES (2161, 57, 'neu', 'new',
'2013-05-22 20:57:12.437383+00', '2013-05-22 20:57:12.656672+00');
INSERT INTO zfvocapp_lessonentry VALUES (2167, 57, 'rot', 'red',
'2013-05-22 21:10:56.728158+00', '2013-05-22 21:10:56.759907+00');
INSERT INTO zfvocapp_lessonentry VALUES (2162, 57, 'alt', 'old',
'2013-05-22 20:57:15.962352+00', '2013-05-22 20:57:15.992568+00');
INSERT INTO zfvocapp_lessonentry VALUES (2166, 57, 'blau', 'blue',
'2013-05-22 21:10:53.223907+00', '2013-05-22 21:10:53.25234+00');
INSERT INTO zfvocapp_lessonentry VALUES (2173, 57, 'gross', 'big',
'2013-05-22 21:12:29.415916+00', '2013-05-22 21:12:29.451332+00');
INSERT INTO zfvocapp_lessonentry VALUES (2168, 57, 'gelb', 'yellow',
'2013-05-22 21:11:02.103493+00', '2013-05-22 21:11:02.136576+00');
INSERT INTO zfvocapp_lessonentry VALUES (2169, 57, 'grün', 'green',
'2013-05-22 21:11:06.374137+00', '2013-05-22 21:11:06.402334+00');
INSERT INTO zfvocapp_lessonentry VALUES (2170, 57, 'braun', 'brown',
'2013-05-22 21:11:10.078453+00', '2013-05-22 21:11:10.106392+00');
INSERT INTO zfvocapp_lessonentry VALUES (2174, 57, 'offen', 'open',
'2013-05-22 21:13:03.851302+00', '2013-05-22 21:13:03.878534+00');
INSERT INTO zfvocapp_lessonentry VALUES (2171, 57, 'grau', 'grey',
'2013-05-22 21:11:13.454313+00', '2013-05-22 21:11:13.485365+00');
INSERT INTO zfvocapp_lessonentry VALUES (2178, 57, 'wach', 'awake',
'2013-05-22 21:14:09.255321+00', '2013-05-22 21:14:09.292234+00');
INSERT INTO zfvocapp_lessonentry VALUES (2175, 57, 'geschlossen',
'closed', '2013-05-22 21:13:08.348016+00', '2013-05-22
21:13:08.376036+00');
INSERT INTO zfvocapp_lessonentry VALUES (2180, 57, 'gesund', 'healthy',
'2013-05-22 21:14:28.173758+00', '2013-05-22 21:14:28.199705+00');
INSERT INTO zfvocapp_lessonentry VALUES (2177, 57, 'traurig', 'sad',
'2013-05-22 21:13:53.405936+00', '2013-05-22 21:13:53.451009+00');
INSERT INTO zfvocapp_lessonentry VALUES (2179, 57, 'müde', 'tired',
'2013-05-22 21:14:11.456667+00', '2013-05-22 21:14:11.484829+00');
INSERT INTO zfvocapp_lessonentry VALUES (2181, 57, 'krank', 'sick',
'2013-05-22 21:14:31.414327+00', '2013-05-22 21:14:31.446299+00');
INSERT INTO zfvocapp_lessonentry VALUES (2182, 57, 'nett', 'nice',
'2013-05-22 21:15:15.143002+00', '2013-05-22 21:15:15.184282+00');
INSERT INTO zfvocapp_lessonentry VALUES (2183, 57, 'lieb', 'dear',
'2013-05-22 21:15:19.547128+00', '2013-05-22 21:15:19.574394+00');
INSERT INTO zfvocapp_lessonentry VALUES (2184, 57, 'schön', 'beautiful',
'2013-05-22 21:15:29.416505+00', '2013-05-22 21:15:29.444392+00');
INSERT INTO zfvocapp_lessonentry VALUES (2185, 57, 'schrecklich', 'awful',
'2013-05-22 21:15:55.308258+00', '2013-05-22 21:15:55.335381+00');
INSERT INTO zfvocapp_lessonentry VALUES (2186, 57, 'weiblich', 'female',
'2013-05-22 21:16:18.967918+00', '2013-05-22 21:16:18.993677+00');
INSERT INTO zfvocapp_lessonentry VALUES (2187, 57, 'männlich', 'male',
'2013-05-22 21:16:21.355328+00', '2013-05-22 21:16:21.387481+00');
INSERT INTO zfvocapp_lessonentry VALUES (2189, 57, 'langsam', 'slow',
'2013-05-22 21:16:40.855376+00', '2013-05-22 21:16:40.889525+00');
INSERT INTO zfvocapp_lessonentry VALUES (2188, 57, 'schnell', 'quick',
'2013-05-22 21:16:37.217384+00', '2013-05-22 21:16:44.05579+00');
INSERT INTO zfvocapp_lessonentry VALUES (2190, 57, 'einfach', 'simple',
'2013-05-22 21:17:13.138712+00', '2013-05-22 21:17:13.164846+00');
INSERT INTO zfvocapp_lessonentry VALUES (2191, 57, 'schwierig',
'difficult', '2013-05-22 21:17:16.858922+00', '2013-05-22
21:17:16.886086+00');

INSERT INTO zfvocapp_wordentry VALUES (4379, 2161, 'neu', 'de',
'2013-05-22 20:57:12.493735+00', '2013-05-22 20:57:12.493775+00');
INSERT INTO zfvocapp_wordentry VALUES (4380, 2161, 'new', 'en',
'2013-05-22 20:57:12.628707+00', '2013-05-22 20:57:12.628734+00');
INSERT INTO zfvocapp_wordentry VALUES (4381, 2162, 'alt', 'de',
'2013-05-22 20:57:15.972969+00', '2013-05-22 20:57:15.972995+00');
INSERT INTO zfvocapp_wordentry VALUES (4382, 2162, 'old', 'en',
'2013-05-22 20:57:15.987178+00', '2013-05-22 20:57:15.987202+00');
INSERT INTO zfvocapp_wordentry VALUES (4383, 2163, 'jung', 'de',
'2013-05-22 20:57:19.782352+00', '2013-05-22 20:57:19.782377+00');
INSERT INTO zfvocapp_wordentry VALUES (4384, 2163, 'young', 'en',
'2013-05-22 20:57:19.795058+00', '2013-05-22 20:57:19.795082+00');
INSERT INTO zfvocapp_wordentry VALUES (4385, 2164, 'schwarz', 'de',
'2013-05-22 21:10:43.807224+00', '2013-05-22 21:10:43.807249+00');
INSERT INTO zfvocapp_wordentry VALUES (4386, 2164, 'black', 'en',
'2013-05-22 21:10:43.834102+00', '2013-05-22 21:10:43.834126+00');
INSERT INTO zfvocapp_wordentry VALUES (4387, 2165, 'weiss', 'de',
'2013-05-22 21:10:47.634643+00', '2013-05-22 21:10:47.634688+00');
INSERT INTO zfvocapp_wordentry VALUES (4388, 2165, 'white', 'en',
'2013-05-22 21:10:47.64728+00', '2013-05-22 21:10:47.647304+00');
INSERT INTO zfvocapp_wordentry VALUES (4389, 2166, 'blau', 'de',
'2013-05-22 21:10:53.233142+00', '2013-05-22 21:10:53.233167+00');
INSERT INTO zfvocapp_wordentry VALUES (4390, 2166, 'blue', 'en',
'2013-05-22 21:10:53.246826+00', '2013-05-22 21:10:53.24685+00');
INSERT INTO zfvocapp_wordentry VALUES (4391, 2167, 'rot', 'de',
'2013-05-22 21:10:56.738268+00', '2013-05-22 21:10:56.738295+00');
INSERT INTO zfvocapp_wordentry VALUES (4392, 2167, 'red', 'en',
'2013-05-22 21:10:56.753734+00', '2013-05-22 21:10:56.753758+00');
INSERT INTO zfvocapp_wordentry VALUES (4393, 2168, 'gelb', 'de',
'2013-05-22 21:11:02.115799+00', '2013-05-22 21:11:02.115828+00');
INSERT INTO zfvocapp_wordentry VALUES (4394, 2168, 'yellow', 'en',
'2013-05-22 21:11:02.129582+00', '2013-05-22 21:11:02.129605+00');
INSERT INTO zfvocapp_wordentry VALUES (4395, 2169, 'grün', 'de',
'2013-05-22 21:11:06.38426+00', '2013-05-22 21:11:06.384285+00');
INSERT INTO zfvocapp_wordentry VALUES (4396, 2169, 'green', 'en',
'2013-05-22 21:11:06.397273+00', '2013-05-22 21:11:06.397297+00');
INSERT INTO zfvocapp_wordentry VALUES (4397, 2170, 'braun', 'de',
'2013-05-22 21:11:10.088019+00', '2013-05-22 21:11:10.088059+00');
INSERT INTO zfvocapp_wordentry VALUES (4398, 2170, 'brown', 'en',
'2013-05-22 21:11:10.10077+00', '2013-05-22 21:11:10.100805+00');
INSERT INTO zfvocapp_wordentry VALUES (4399, 2171, 'grau', 'de',
'2013-05-22 21:11:13.464967+00', '2013-05-22 21:11:13.465002+00');
INSERT INTO zfvocapp_wordentry VALUES (4400, 2171, 'grey', 'en',
'2013-05-22 21:11:13.47939+00', '2013-05-22 21:11:13.479414+00');
INSERT INTO zfvocapp_wordentry VALUES (4401, 2172, 'klein', 'de',
'2013-05-22 21:12:27.254657+00', '2013-05-22 21:12:27.254682+00');
INSERT INTO zfvocapp_wordentry VALUES (4402, 2172, 'small', 'en',
'2013-05-22 21:12:27.276567+00', '2013-05-22 21:12:27.276591+00');
INSERT INTO zfvocapp_wordentry VALUES (4403, 2173, 'gross', 'de',
'2013-05-22 21:12:29.428584+00', '2013-05-22 21:12:29.42861+00');
INSERT INTO zfvocapp_wordentry VALUES (4404, 2173, 'big', 'en',
'2013-05-22 21:12:29.446156+00', '2013-05-22 21:12:29.446179+00');
INSERT INTO zfvocapp_wordentry VALUES (4405, 2174, 'offen', 'de',
'2013-05-22 21:13:03.860215+00', '2013-05-22 21:13:03.86024+00');
INSERT INTO zfvocapp_wordentry VALUES (4406, 2174, 'open', 'en',
'2013-05-22 21:13:03.872967+00', '2013-05-22 21:13:03.872992+00');
INSERT INTO zfvocapp_wordentry VALUES (4407, 2175, 'geschlossen', 'de',
'2013-05-22 21:13:08.35745+00', '2013-05-22 21:13:08.357475+00');
INSERT INTO zfvocapp_wordentry VALUES (4408, 2175, 'closed', 'en',
'2013-05-22 21:13:08.370163+00', '2013-05-22 21:13:08.370187+00');
INSERT INTO zfvocapp_wordentry VALUES (4409, 2176, 'glücklich', 'de',
'2013-05-22 21:13:50.668264+00', '2013-05-22 21:13:50.668289+00');
INSERT INTO zfvocapp_wordentry VALUES (4410, 2176, 'happy', 'en',
'2013-05-22 21:13:50.681382+00', '2013-05-22 21:13:50.681406+00');
INSERT INTO zfvocapp_wordentry VALUES (4411, 2177, 'traurig', 'de',
'2013-05-22 21:13:53.415872+00', '2013-05-22 21:13:53.415896+00');
INSERT INTO zfvocapp_wordentry VALUES (4412, 2177, 'sad', 'en',
'2013-05-22 21:13:53.444658+00', '2013-05-22 21:13:53.444682+00');
INSERT INTO zfvocapp_wordentry VALUES (4413, 2178, 'wach', 'de',
'2013-05-22 21:14:09.265285+00', '2013-05-22 21:14:09.265311+00');
INSERT INTO zfvocapp_wordentry VALUES (4414, 2178, 'awake', 'en',
'2013-05-22 21:14:09.285589+00', '2013-05-22 21:14:09.285613+00');
INSERT INTO zfvocapp_wordentry VALUES (4415, 2179, 'müde', 'de',
'2013-05-22 21:14:11.467629+00', '2013-05-22 21:14:11.467653+00');
INSERT INTO zfvocapp_wordentry VALUES (4416, 2179, 'tired', 'en',
'2013-05-22 21:14:11.479953+00', '2013-05-22 21:14:11.479977+00');
INSERT INTO zfvocapp_wordentry VALUES (4417, 2180, 'gesund', 'de',
'2013-05-22 21:14:28.18266+00', '2013-05-22 21:14:28.182686+00');
INSERT INTO zfvocapp_wordentry VALUES (4418, 2180, 'healthy', 'en',
'2013-05-22 21:14:28.194698+00', '2013-05-22 21:14:28.194722+00');
INSERT INTO zfvocapp_wordentry VALUES (4419, 2181, 'krank', 'de',
'2013-05-22 21:14:31.425494+00', '2013-05-22 21:14:31.425519+00');
INSERT INTO zfvocapp_wordentry VALUES (4420, 2181, 'sick', 'en',
'2013-05-22 21:14:31.439754+00', '2013-05-22 21:14:31.439778+00');
INSERT INTO zfvocapp_wordentry VALUES (4421, 2182, 'nett', 'de',
'2013-05-22 21:15:15.163646+00', '2013-05-22 21:15:15.16367+00');
INSERT INTO zfvocapp_wordentry VALUES (4422, 2182, 'nice', 'en',
'2013-05-22 21:15:15.177561+00', '2013-05-22 21:15:15.177585+00');
INSERT INTO zfvocapp_wordentry VALUES (4423, 2183, 'lieb', 'de',
'2013-05-22 21:15:19.557155+00', '2013-05-22 21:15:19.55718+00');
INSERT INTO zfvocapp_wordentry VALUES (4424, 2183, 'dear', 'en',
'2013-05-22 21:15:19.569411+00', '2013-05-22 21:15:19.569435+00');
INSERT INTO zfvocapp_wordentry VALUES (4425, 2184, 'schön', 'de',
'2013-05-22 21:15:29.426358+00', '2013-05-22 21:15:29.426389+00');
INSERT INTO zfvocapp_wordentry VALUES (4426, 2184, 'beautiful', 'en',
'2013-05-22 21:15:29.439535+00', '2013-05-22 21:15:29.439567+00');
INSERT INTO zfvocapp_wordentry VALUES (4427, 2185, 'schrecklich', 'de',
'2013-05-22 21:15:55.318041+00', '2013-05-22 21:15:55.318066+00');
INSERT INTO zfvocapp_wordentry VALUES (4428, 2185, 'awful', 'en',
'2013-05-22 21:15:55.330489+00', '2013-05-22 21:15:55.330513+00');
INSERT INTO zfvocapp_wordentry VALUES (4429, 2186, 'weiblich', 'de',
'2013-05-22 21:16:18.976889+00', '2013-05-22 21:16:18.976914+00');
INSERT INTO zfvocapp_wordentry VALUES (4430, 2186, 'female', 'en',
'2013-05-22 21:16:18.988711+00', '2013-05-22 21:16:18.988735+00');
INSERT INTO zfvocapp_wordentry VALUES (4431, 2187, 'männlich', 'de',
'2013-05-22 21:16:21.367447+00', '2013-05-22 21:16:21.367472+00');
INSERT INTO zfvocapp_wordentry VALUES (4432, 2187, 'male', 'en',
'2013-05-22 21:16:21.380302+00', '2013-05-22 21:16:21.380326+00');
INSERT INTO zfvocapp_wordentry VALUES (4433, 2188, 'schnell', 'de',
'2013-05-22 21:16:37.228106+00', '2013-05-22 21:16:37.22813+00');
INSERT INTO zfvocapp_wordentry VALUES (4434, 2188, 'fast', 'en',
'2013-05-22 21:16:37.24008+00', '2013-05-22 21:16:37.240104+00');
INSERT INTO zfvocapp_wordentry VALUES (4435, 2189, 'langsam', 'de',
'2013-05-22 21:16:40.868826+00', '2013-05-22 21:16:40.868851+00');
INSERT INTO zfvocapp_wordentry VALUES (4436, 2189, 'slow', 'en',
'2013-05-22 21:16:40.884681+00', '2013-05-22 21:16:40.884705+00');
INSERT INTO zfvocapp_wordentry VALUES (4437, 2188, 'quick', 'en',
'2013-05-22 21:16:44.041216+00', '2013-05-22 21:16:44.041242+00');
INSERT INTO zfvocapp_wordentry VALUES (4438, 2190, 'einfach', 'de',
'2013-05-22 21:17:13.147882+00', '2013-05-22 21:17:13.147906+00');
INSERT INTO zfvocapp_wordentry VALUES (4439, 2190, 'simple', 'en',
'2013-05-22 21:17:13.159739+00', '2013-05-22 21:17:13.159764+00');
INSERT INTO zfvocapp_wordentry VALUES (4440, 2191, 'schwierig', 'de',
'2013-05-22 21:17:16.86852+00', '2013-05-22 21:17:16.868544+00');
INSERT INTO zfvocapp_wordentry VALUES (4441, 2191, 'difficult', 'en',
'2013-05-22 21:17:16.881102+00', '2013-05-22 21:17:16.881126+00');
}}}

if that doesn't help i can also give you access to the database

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:18>

Django

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May 24, 2013, 5:01:10 AM5/24/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------

Reporter: av@… | Owner: nobody
Type: Bug | Status: new

Comment (by lukeplant):

Thank you kenn, that's brilliant! I have at last been able to reproduce
the bug in test case form using this data, and I'll hopefully get it fixed
soon.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:19>

Django

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May 24, 2013, 6:22:50 AM5/24/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody
Type: Bug | Status: closed

Component: Database layer | Version: 1.4

(models, ORM) | Resolution: fixed

Changes (by Luke Plant <L.Plant.98@…>):

* status: new => closed

* resolution: => fixed

Comment:

In [changeset:"4fd94969d859eb25680a5a52ed482c8f22e5ee15"]:
{{{
#!CommitTicketReference repository=""
revision="4fd94969d859eb25680a5a52ed482c8f22e5ee15"
Fixed #19607 - prefetch_related crash

Thanks to a...@rdf.ru and flar...@yahoo.de for the report.
}}}

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:20>

Django

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Jul 12, 2013, 8:17:50 PM7/12/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody

Comment (by tswaterman):

thanks! this one was confusing me to no end.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:21>

Django

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Jul 24, 2013, 4:18:22 PM7/24/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody

Comment (by npinchot):

Any chance this fix will be merged into Django 1.5.2?

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:22>

Django

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Jul 27, 2013, 3:22:57 AM7/27/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody

Comment (by ppetrid):

I would also appreciate merging this fix into Django 1.5.x

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:23>

Django

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Jul 27, 2013, 6:45:34 PM7/27/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody

Comment (by Tim Graham <timograham@…>):

In [changeset:"00b39e0145c5b9117503b20bba74948294a30e5a"]:
{{{
#!CommitTicketReference repository=""
revision="00b39e0145c5b9117503b20bba74948294a30e5a"
[1.5.x] Fixed #19607 - prefetch_related crash

Thanks to a...@rdf.ru and flar...@yahoo.de for the report.

Backport of 4fd94969d8 from master
}}}

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:24>

Django

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Aug 22, 2013, 1:23:54 PM8/22/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody

Comment (by Ry4an):

I don't suppose anyone's considering backporting this to 1.4? We're not
yet ready to upgrade, but running into this in production.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:25>

Django

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Aug 22, 2013, 1:30:52 PM8/22/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 1.4
(models, ORM) | Resolution: fixed
Severity: Normal | Triage Stage:
Keywords: prefetch | Unreviewed
prefetch_related | Needs documentation: 0
Has patch: 1 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
-------------------------------------+-------------------------------------

Comment (by timo):

Sorry, per our [https://docs.djangoproject.com/en/dev/internals/release-
process/#supported-versions supported versions] policy, 1.4 is only
receiving security updates at this point.

--
Ticket URL: <https://code.djangoproject.com/ticket/19607#comment:26>

Django

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Aug 22, 2013, 3:50:30 PM8/22/13

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#19607: prefetch_related crash
-------------------------------------+-------------------------------------
Reporter: av@… | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 1.4
(models, ORM) | Resolution: fixed
Severity: Normal | Triage Stage:
Keywords: prefetch | Unreviewed
prefetch_related | Needs documentation: 0
Has patch: 1 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
-------------------------------------+-------------------------------------

Comment (by Ry4an):

Replying to [comment:26 timo]:

> Sorry, per our [https://docs.djangoproject.com/en/dev/internals/release-
process/#supported-versions supported versions] policy, 1.4 is only
receiving security updates at this point.

[Django] #19607: prefetch_related bug

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