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Code Issues 32 Releases Wiki Activity

Fixed #20849 -- ModelForms do not work well with prefetch_related.

Browse Source 
model_to_dict() (used when rendering forms) queries the database
to get the list of primary keys for ManyToMany fields. This is
unnecessary if the field queryset has been prefetched, all the
keys are already in memory and can be obtained with a simple
iteration.
This commit is contained in:
Jim Bailey
2013-11-01 12:55:35 +00:00
committed by Anssi Kääriäinen
parent 4202d9cf0c
commit 539e3693d4
2 changed files with 40 additions and 1 deletions
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6
django/forms/models.py
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@@ -134,7 +134,11 @@ def model_to_dict(instance, fields=None, exclude=None):
data[f.name] = []
else:
# MultipleChoiceWidget needs a list of pks, not object instances.
data[f.name] = list(f.value_from_object(instance).values_list('pk', flat=True))
qs = f.value_from_object(instance)
if qs._result_cache is not None:
data[f.name] = [item.pk for item in qs]
else:
data[f.name] = list(qs.values_list('pk', flat=True))
else:
data[f.name] = f.value_from_object(instance)
return data