#21956: Inconsistent behaviour of Q objects
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Reporter: debanshuk | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: 1.5
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Suppose we have a contact model with following definition:
{{{
class Contact(models.Model):
name = models.CharField()
company_uid = models.IntegerField(null=True, blank=True)
}}}
Consider following two queries:
`Contact.objects.filter(~(Q(name='ABC') | Q(company_uid=5)))`
`Contact.objects.filter(~Q(name='ABC') & ~Q(company_uid=5))`
These queries are exactly the same, right? Just used DeMorgan's law i.e
"not (A or B)" is the same as "(not A) and (not B)". But the generated SQL
of these queries says something else:
`SELECT "profiles_contact"."id", "profiles_contact"."name",
"profiles_contact"."company_uid" FROM "profiles_contact" WHERE NOT
(("profiles_contact"."name" = ABC OR "profiles_contact"."company_uid" = 5
))`
`SELECT "profiles_contact"."id", "profiles_contact"."name",
"profiles_contact"."company_uid" FROM "profiles_contact" WHERE (NOT
("profiles_contact"."name" = ABC ) AND NOT
(("profiles_contact"."company_uid" = 5 AND
"profiles_contact"."company_uid" IS NOT NULL)))`
(The desired query is the one with `IS NOT NULL` condition)
This issue only exists till version 1.5, it has been fixed in Django-1.6.
There is already a closed bug
(https://code.djangoproject.com/ticket/21192) which was similar to this
one. The bug was closed stating that the issue has been fixed in
Django-1.6 and changes required to back-patch the fixes to 1.5 are just
too big. But I believe this issue is more severe than the issue stated the
that bug, as it is a more general case and should be back-patched to 1.5
and older version too.
--
Ticket URL: <https://code.djangoproject.com/ticket/21956>
Django <https://code.djangoproject.com/>
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