#9759: exclude() does not return the opposite of filter() for one to many
relationships
------------------------------------------+---------------------------------
Reporter: gregplaysguitar | Owner: nobody
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: 1.0
Keywords: "not equal", exclude, filter | Stage: Unreviewed
Has_patch: 0 |
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Consider the following models (in an app called "news"):
{{{
class Region(models.Model):
name = models.CharField(max_length=255)
class Career(AuditedBaseModel):
name = models.CharField(max_length=255)
region = models.ForeignKey(Region)
}}}
I'm trying to select all regions that have at least one career, using:
{{{
Region.objects.exclude(career=None)
}}}
but I'm getting no results. The opposite - retrieving all regions with no
career - works fine:
{{{
Region.objects.filter(career=None)
}}}
The filter() call above uses the following sql:
{{{
SELECT "news_region"."id", "news_region"."name"
FROM "news_region"
LEFT OUTER JOIN "news_career" ON ("news_region"."id" =
"news_career"."region_id")
WHERE "news_career"."id" IS NULL;
}}}
and the exclude() uses:
{{{
SELECT "news_region"."id", "news_region"."name"
FROM "news_region"
WHERE NOT (
"news_region"."id" IN (
SELECT U1."region_id"
FROM "news_region" U0
LEFT OUTER JOIN "news_career" U1 ON (U0."id" = U1."region_id")
WHERE U1."id" IS NULL
)
);
}}}
which doesn't work. I guess there's reasons for it to be done this way,
but if exclude actually just wrapped the filter() clause in a NOT(), ie:
{{{
SELECT "news_region"."id", "news_region"."name"
FROM "news_region"
LEFT OUTER JOIN "news_career" ON ("news_region"."id" =
"news_career"."region_id")
WHERE NOT("news_career"."id" IS NULL);
}}}
it would work fine. Also, the presence of a "not equal" operator would
solve my problem.
--
Ticket URL: <http://code.djangoproject.com/ticket/9759>
Django <http://code.djangoproject.com/>
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