#4102: Allow UPDATE of only specific fields in model.save()
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Reporter: Collin Grady | Owner: cgrady
<cgrady@…> | Status: new
Type: New feature | Version: SVN
Component: Database layer | Resolution:
(models, ORM) | Triage Stage: Accepted
Severity: Normal | Needs documentation: 1
Keywords: update fields sql | Patch needs improvement: 1
row table modified | UI/UX: 0
Has patch: 1 |
Needs tests: 1 |
Easy pickings: 0 |
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Changes (by akaariai):
* needs_tests: 0 => 1
Comment:
A couple of design considerations:
- if only fields is given should it imply force_update=True. My take is
yes, as I don't think there will be a use case for only_fields + insert.
Set the field values to NULL instead. In addition only_fields + insert
could lead to some complicated situations. So, maybe the kwarg should
instead be update_fields?
- what if the model does not have fields given in the update_fields
argument? Should it be an error or not. I guess erroring out could be
wise, as otherwise this could hide data loss bugs. This should probably be
done in .save() as a pre-check, and then .save_base just uses the given
set without further checks.
- It might make sense to add the field set to pre/post save signals as
an argument if this is doable from backwards compatibility viewpoint.
- Should a deferred model which is then saved have automatically
update_fields set so that only the non-deferred fields will be saved. I
think currently the fields are loaded from the database and then the
update will update the fields to the just fetched values which does not
make sense.
This should be tested with model inheritance, too. It is a common pain-
point for this kind of feature. The current test doesn't actually seem to
test that the name is updated, so in general more tests needed.
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Ticket URL: <https://code.djangoproject.com/ticket/4102#comment:75>
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