#34871: Validation of UniqueConstraint with Case() crashes.
-------------------------------------+-------------------------------------
Reporter: Andrew Roberts | Owner: Francesco
| Panico
Type: Bug | Status: assigned
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Simon Charette):
I would suggest using a `Func` instead of `Case` / `When` or `Q` if you
really need to achieve the exact SQL that `CASE WHEN` would generated
Something like
{{{#!python
models.UniqueConstraint(
Func(F("email")), template="CASE WHEN active = true THEN
%(expressions)s END"),
name="unique_active_email",
)
}}}
Or to simply use `UniqueConstraint.condition` as
[https://docs.djangoproject.com/en/5.0/ref/models/constraints/#condition
documented] if the backend you use support it which will also incur less
storage use.
{{{#!python
models.UniqueConstraint(
fields=["email"],
name="unique_active_email",
condition=Q(active=True),
)
}}}
I think we should spend the time to implement `Q.replace_expressions`
though as it's pretty trivial to do so and would cover for the cases that
cannot be expressed using `.condition` such as `CASE WHEN last_name IS
NULL THEN first_name ELSE first_name || last_name END`.
--
Ticket URL: <https://code.djangoproject.com/ticket/34871#comment:9>
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