#14609: __or__ method of queries does not return a correctly combined query.
-------------------------------------+-------------------------------------
Reporter: melinath | Owner: nobody
Status: new | Milestone:
Component: Database | Version: 1.2
layer (models, ORM) | Keywords:
Resolution: | Has patch: 0
Triage Stage: Accepted | Needs tests: 0
Needs documentation: 0 |
Patch needs improvement: 0 |
-------------------------------------+-------------------------------------
Comment (by hvdklauw):
Ran into this problem two, tried to work around it with Q objects; still
didn't work
{{{
class EntityManager(models.Manager):
def between(self, entity1, entity2):
"""
Returns a queryset that shows entities between the two given
entities
"""
result =
self.get_query_set().filter(related_to__to_entity=entity1).filter(related_from__from_entity=entity2)
| \
self.get_query_set().filter(related_to__to_entity=entity2).filter(related_from__from_entity=entity1)
| \
self.get_query_set().filter(related_from__from_entity=entity1).filter(related_from__from_entity=entity2)
| \
self.get_query_set().filter(related_to__to_entity=entity1).filter(related_to__to_entity=entity2)
return result
def between2(self, entity1, entity2):
from django.db.models import Q
result = self.get_query_set().filter(
(
Q(
related_to__to_entity=entity1
) & Q(
related_from__from_entity=entity2
)
) |
(
Q(
related_to__to_entity=entity2
) & Q(
related_from__from_entity=entity1
)
) |
(
Q(
related_from__from_entity=entity1
) & Q(
related_from__from_entity=entity1
)
) |
(
Q(
related_to__to_entity=entity1
) & Q(
related_to__to_entity=entity2
)
)
)
return result
class Entity(models.Model):
"""
Entity
"""
name = models.CharField(_('naam'), max_length=250)
objects = EntityManager()
class Relation(models.Model):
"""
Relation
"""
from_entity = models.ForeignKey(Entity, related_name='related_to',
verbose_name=_('van entiteit'))
to_entity = models.ForeignKey(Entity, related_name='related_from',
verbose_name=_('naar entiteit'))
}}}
Resulting query for between is:
{{{
SELECT "entities_entity"."id", "entities_entity"."name",
"entities_entity"."entity_type_id"
FROM "entities_entity"
INNER JOIN "entities_relation" ON ("entities_entity"."id" =
"entities_relation"."from_entity_id")
INNER JOIN "entities_relation" T4 ON ("entities_entity"."id" =
T4."to_entity_id")
LEFT OUTER JOIN "entities_relation" T6 ON ("entities_entity"."id" =
T6."to_entity_id")
LEFT OUTER JOIN "entities_relation" T7 ON ("entities_entity"."id" =
T7."from_entity_id")
WHERE (("entities_relation"."to_entity_id" = 1 AND T4."from_entity_id" =
3 )
OR ("entities_relation"."to_entity_id" = 3 AND
T4."from_entity_id" = 1 )
OR (T4."from_entity_id" = 1 AND T6."from_entity_id" = 3 )
OR ("entities_relation"."to_entity_id" = 1 AND T7."to_entity_id"
= 3 ))
}}}
The problem are the two INNER JOINS I get the expected result when they
are also LEFT (OUTER) JOINS
The Q solution gives me this query:
{{{
SELECT "entities_entity"."id", "entities_entity"."name",
"entities_entity"."entity_type_id"
FROM "entities_entity"
LEFT OUTER JOIN "entities_relation" ON ("entities_entity"."id" =
"entities_relation"."from_entity_id")
LEFT OUTER JOIN "entities_relation" T4 ON ("entities_entity"."id" =
T4."to_entity_id")
WHERE (("entities_relation"."to_entity_id" = 1 AND T4."from_entity_id" =
3 )
OR ("entities_relation"."to_entity_id" = 3 AND
T4."from_entity_id" = 1 )
OR (T4."from_entity_id" = 1 AND T4."from_entity_id" = 1 )
OR ("entities_relation"."to_entity_id" = 1 AND
"entities_relation"."to_entity_id" = 3 ))
}}}
Which gives me too many results
--
Ticket URL: <http://code.djangoproject.com/ticket/14609#comment:2>
Django <http://code.djangoproject.com/>
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