#28344: Add for_update parameter to Model.refresh_from_db()
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Reporter: Patryk Zawadzki | Owner: (none)
Type: New feature | Status: new
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Aivars KalvÄns):
Replying to [comment:3 Simon Charette]:
> I fear we might open a can of worms here and have to either say no to
`nowait`, `skip_locked` and now `of` support in the future or allow
`for_update` to be a dict delegating kwargs to the underlying
`select_for_update()` call.
I think most of those parameters do not apply to operations on the
specific model:
`of` when multiple models have to be locked, a QuerySet should be the
right choice
`skip_locked` does not make sense when working with one specific instance
of Model (primary key)
`nowait` might be interesting - something similar to
`threading.Lock.acquire(blocking=False)`. But unlike `acquire` which
returns a boolean, `select_for_update` raises `DatabaseError`. Raising an
exception from `refresh_from_db` would suggest the object is in an invalid
state. Code that uses the object after the exception would raise eyebrows
during code review. Making `refresh_from_db` return a boolean indicating
if it succeeded or not could also lead to issues because people are not
used to checking the result of `refresh_from_db`.
So I think the default `select_for_update` is the only right solution.
Adding `nowait` might be an option together with a new dedicated method
`refresh_for_update` but I haven't seen use for that in my domain.
--
Ticket URL: <https://code.djangoproject.com/ticket/28344#comment:25>
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