#36398: select_for_update(of=...) ignores "self" when using values_list() when
not
selecting a column from the model
-------------------------------------+-------------------------------------
Reporter: OutOfFocus4 | Owner:
| JakeWalson
Type: Bug | Status: assigned
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by OutOfFocus4):
Replying to [comment:8 Sarah Boyce]:
> This won't be resolved until someone fixes the ticket, so there's no
need to confirm with each release that this is still open (that the ticket
is open is enough to confirm that this should still be an open issue)
>
> We also wouldn't backport a fix into 5.2 unless this is a bug that was
introduced by 5.2. If you believe this was introduced in 5.2, you can do a
git bisect to find the commit that introduces this issue. This would
increase the priority of the ticket.
I can replicate this issue with older versions of Django, so I don't
believe this was introduced in 5.2.
I believe I may have found (part of) the cause. From
https://github.com/django/django/blob/d82f25d3f0f4eb7be721a72d0e79a8d13d394d32/django/db/models/sql/compiler.py#L1432C1-L1443C56:
{{{#!python
def _get_first_selected_col_from_model(klass_info):
"""
Find the first selected column from a model. If it doesn't
exist,
don't lock a model.
select_fields is filled recursively, so it also contains
fields
from the parent models.
"""
concrete_model = klass_info["model"]._meta.concrete_model
for select_index in klass_info["select_fields"]:
if self.select[select_index][0].target.model ==
concrete_model:
return self.select[select_index][0]
}}}
If the docstring is to be believed, only tables whose columns are in the
query's `SELECT` can be locked. I do not know enough about Django's
internals to know if that is what the function actually does.
--
Ticket URL: <https://code.djangoproject.com/ticket/36398#comment:9>
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