#25643: Extend expressions API to update()
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Reporter: jorgecarleitao | Owner: nobody
Type: New feature | Status: new
Component: Database layer (models, ORM) | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Given the following models:
{{{
class Relation(models.Model):
rating = models.IntegerField(default=0)
class SignRelation(models.Model):
relation = models.ForeignKey(Relation, related_name='sign_relations')
rating = models.IntegerField(default=0)
}}}
support queries like
{{{
Relation.objects.update(rating=Sum('sign_relations__rating'))
Relation.objects.annotate(total_rating=Sum('sign_relations__rating')).update(rating=F('total_rating'))
}}}
to avoid queries like
{{{
for relation in
Relation.objects.annotate(total_rating=Sum('sign_relations__rating')):
relation.rating = relation.total_rating or 0
relation.save()
}}}
This is useful to populate models that contain redundant data.
Based on [http://stackoverflow.com/questions/3652736/django-update-
queryset-with-annotation this question] in SO.
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Ticket URL: <https://code.djangoproject.com/ticket/25643>
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