#33516: QuerySet update() under postgres with
select_for_update(skip_locked=True)
results in neither FOR UPDATE nor SKIP LOCKED
-------------------------------------+-------------------------------------
Reporter: Grant Gainey | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 3.2
(models, ORM) |
Severity: Normal | Resolution: invalid
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):
* status: new => closed
* resolution: => invalid
Comment:
In the latest version of Django
[https://github.com/django/django/blob/7119f40c9881666b6f9b5cf7df09ee1d21cc8344/django/db/models/sql/query.py#L2161-L2171
the ordering should not be cleared] when `select_for_update` is used on
the subquery provided to a `__in` lookup.
{{{#!python
def update_timestamp(index):
content_q = (
TestModel.objects.order_by("pk")
.select_for_update(skip_locked=True)
.values_list("pk", flat=True)
)
TestModel.objects.filter(pk__in=content_q).update(timestamp_of_interest=now())
}}}
There was some recent changes in this area in 4.0 and I haven't confirmed
if this is an issue on 3.2 but in all cases `order_by.select_for_update`
has to be called on the subquery and not the outer one for this to work as
the resulting SQL hints at and that's likely why your solution isn't
working here.
--
Ticket URL: <https://code.djangoproject.com/ticket/33516#comment:1>
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