#30484: Using RawSQL with CheckConstraint
-------------------------------------+-------------------------------------
Reporter: David Sanders | Owner: nobody
Type: New feature | Status: closed
Component: Database layer | Version: 2.2
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):
* status: new => closed
* resolution: => wontfix
Comment:
It looks like this could be expressed as
`Q(total__isnull=RawSQL('(total_last_updated IS NULL)')` but I haven't
tested it.
When #25367 lands it should even work without `RawSQL`:
`Q(total__isnull=Q(total_last_updated__isnull=True))`.
In the mean time if the above doesn't work I'd suggest you register
[https://docs.djangoproject.com/en/2.2/howto/custom-lookups/ a custom
Lookup] to express this filtering.
{{{#!python
from django.db.models.fields import Field
from django.db.models import Lookup
class IsNullEq(Lookup):
lookup_name = 'isnulleq'
def as_sql(self, compiler, connection):
lhs, lhs_params = self.process_lhs(compiler, connection)
rhs, rhs_params = self.process_rhs(compiler, connection)
params = lhs_params + rhs_params
return '(%s IS NULL) = (%s IS NULL)' % (lhs, rhs), params
Field.register_lookup(IsNullEq)
}}}
And use it for your constraint's condition
`Q(total__isnulleq=F('total_last_updated'))`.
--
Ticket URL: <https://code.djangoproject.com/ticket/30484#comment:2>
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