#36683: Update with Distinct Produces Unintentional Results
-------------------------------------+-------------------------------------
Reporter: matthewshirley | Type: Bug
Status: new | Component: Database
| layer (models, ORM)
Version: 5.2 | Severity: Normal
Keywords: orm,distinct,update | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Similar to #32433.
The ORM permits calling `update()` on a `Queryset` when a `distinct()` was
applied. This results in unforeseen consequences where a larger data set
will be updated than what is expected. Similar to the example provided in
#32433:
`Comment.objects.order_by('post_id',
'created_at').distinct('post_id').update(deleted=True)`
The developer may assume that this will delete only one comment per
`post_id`, however, the `distinct()` is ignored (as `UPDATE` has no
distinct) which results in the entire table being updated:
`UPDATE "post_comment" SET "deleted" = true'`
Since `delete()` already guards against this case, I believe `update()`
should behave consistently to protect the developer from mistakes, even
though applying a `distinct()` before an `update()` is generally unusual.
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Ticket URL: <https://code.djangoproject.com/ticket/36683>
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