#18306: Deferred models should automatically issue update_fields when saving
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Reporter: akaariai | Owner: akaariai
Type: | Status: reopened
Cleanup/optimization | Version: master
Component: Database layer | Resolution:
(models, ORM) | Triage Stage: Ready for
Severity: Normal | checkin
Keywords: | Needs documentation: 0
Has patch: 1 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
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Comment (by akaariai):
The problem I faced was that there were multiple places in models/query.py
where the deferred_fields would need to be calculated. The original
implementation didn't take into account select_related (where
get_cached_row() can return deferred instances), and qs.raw(). These just
work with the current implementation. In addition, there is no additional
state bookkeeping which is always a bonus. One less place for bugs to hide
:)
If one wants to do dirty field state tracking, the solution is to use the
model instance itself or it's state to keep the dirty field info, and then
just overrider the .save() method and use update_fields in there for the
dirty fields.
BTW I have been wondering if we should allow 'pk' in the update_fields. If
you say `"update_fields=['pk']"`, then the primary key will be updated as
part of the query. I know there is no cascade support in Django, but one
can always use custom db schemas and ON UPDATE CASCADE. Seems useful to
me. But of course not this ticket's problem...
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Ticket URL: <https://code.djangoproject.com/ticket/18306#comment:20>
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