#21144: Not possible to update foreign key by id for a queryset
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Reporter: dakinsloss@… | Owner: nobody
Type: | Status: new
Cleanup/optimization | Version: 1.5
Component: Database layer | Keywords: update, related model,
(models, ORM) | performance
Severity: Normal | Has patch: 0
Triage Stage: Unreviewed | UI/UX: 0
Easy pickings: 0 |
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Attempting to minimize queries when updating list of ModelA instances that
have foreign keys to ModelB, and I know the ids of the new ModelB
instances I want to use for the instances of ModelA (that I only have the
id for, not the instance).
Trying:
ModelA.objects.filter(pk=id_of_a_instance).update(b_id=id_of_b_instance)
which yields 'FieldNameDoesNotExist' because 'get_field_by_name' only has
'b' as a field name for ModelA, not b_id (which is strange given that is
what is actually stored).
Then I try:
ModelA.objects.filter(pk=id_of_a_instance).update(b=id_of_b_instance),
which says it needs an instance of ModelB, not a number.
Which means I will be stuck with an extra query:
model_b_list = list(ModelB.objects.filter(id_in=[list of ids for a
instances])
and then have to iterate through the ModelA instances and assign the
actual ModelB instances
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Ticket URL: <https://code.djangoproject.com/ticket/21144>
Django <https://code.djangoproject.com/>
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