#16549: In Django models, modified-rows count would help in handling optimistic
concurrency control problems
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Reporter: | Owner: nobody
estebistec | Status: new
Type: New | Component: Database layer
feature | (models, ORM)
Milestone: | Severity: Normal
Version: 1.3 | Keywords:
Resolution: | Has patch: 0
Triage Stage: Design | Needs tests: 0
decision needed | Easy pickings: 0
Needs documentation: 0 |
Patch needs improvement: 0 |
UI/UX: 0 |
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Comment (by akaariai):
One can implement any logic in the signal callback. But it does take too
much work to implement such a field. Also, relying on catching the
exceptions from the save is just plain wrong (it results in transaction
commit all too easily). The optimistic lock check should be done in model
validation if possible.
A conditional save would be handy. But it is not trivial to implement. The
implementation should be one that handles derived classes, does not easily
lead to half-updates (the condition was ok for the first table in derived
save, but not for the second) and does not lead to too much code
duplication. Having two different versions of base_save does not look
appealing. Are there enough use cases that are not solvable by overriding
the save() method or signals?
It is a good idea to return models.UPDATED or models.INSERTED from save(),
returning models.DELETED or models.NO_ACTION from delete() and modified
object counts from qs.update(), qs.delete(). Row counts instead of object
counts from qs.update() and qs.delete() is a bit harder problem. The
object count would not include related models deleted or updated. The
return values from save() and delete() are just examples.
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Ticket URL: <https://code.djangoproject.com/ticket/16549#comment:10>
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