#27365: Fields suddenly not found.
-------------------------------------+-------------------------------------
Reporter: Brandon | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.9
(models, ORM) |
Severity: Normal | Resolution:
Keywords: FieldDoesNotExist | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Brandon):
* status: closed => new
* resolution: needsinfo =>
Comment:
After stepping completely through the call stack down from
{{{MySubclassOfaModelSubclass.objects.filter(id=1234)}}} we arrive at
{{{get_related_field}}} in reverse_related.py Line# 237
The call in this function that fails is {{{field =
self.model._meta.get_field(self.field_name)}}}
It fails because {{{self.field_name}}} has somehow been set to
{{{self.name}}}.
I cannot directly reproduce the error on demand. But setting
{{{self.field_name = self.name}}} from a breakpoint at Line# 237
reproduces *exactly* the stack trace I am (and have been) receiving on
multiple independent production instances running first under
Apache+mod_wsgi then nginx+uWSGI since moving from 1.7 to 1.9 months ago.
I replicated the production stack trace via pudb checking every function
scoped local variable along the way against a production stack trace that
logged those variables on a failure. I checked them down from
{{{.filter}}} to {{{.get_related_field}}}; all populated variables are
identical down the complete call stack. The only way to reproduce that
complete call stack and exact exception is to set {{{self.field_name =
self.name}}} where {{{self}}} is a {{{OneToOneRel}}} representing
{{{MySubclassOfaModelSubclass}}} - note that it actually shows up from
repr as {{{<OneToOneRel: myapp.mysubclassofamodelsubclass>}}}
I apologize for continually reopening this ticket. If there is another (or
better) avenue to continue delivering detail around this issue, I'm
certainly open to it. This has been a major thorn in my side. I'll provide
any and all information necessary to get to the bottom of this very subtle
and difficult issue. I'll be happy to work-up and submit a patch once the
root cause is located.
Thanks,
--Brandon
P.S. Please note that it is not just
{{{MySubclassOfaModelSubclass.objects.filter(id=1234)}}} that fails. Any
forward FK relation can fail (so
{{{MySubclassOfaModelSubclass.objects.filter(foo_id=55)}}}) - and fails in
exactly the same way. The MySubclassOfaModelSubclass class has many
forward FKs in it. It doesn't seem to matter which FK field is accessed,
the stack trace is always the same.
--
Ticket URL: <https://code.djangoproject.com/ticket/27365#comment:10>
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