#33996: Inconsistent behavior of CheckConstraints validation on None values.
-------------------------------------+-------------------------------------
Reporter: James Beith | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 4.1
(models, ORM) |
Severity: Release blocker | 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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Changes (by David Sanders):
* cc: David Sanders (added)
Comment:
Aha I'd also just noticed this behaviour.
It's due to the check constraint doing the validation in the WHERE clause
of a query… a NULL value producing an empty resultset hence failing the
validation:
{{{
SELECT 1 AS "_check" WHERE NULL >= 0
}}}
The original PR for this feature mentions moving to WHERE from SELECT to
get around certain issue – which is somewhat unfortunate because using
SELECT could've given the opportunity to check the result against false.
My naive suggestion would be to add an |Q(field=None) against nullable
fields in the check's query.
--
Ticket URL: <https://code.djangoproject.com/ticket/33996#comment:2>
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