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#4917 - Remove O(n) queries in m2m updates #5093

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#4917 - Remove O(n) queries in m2m updates #5093

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#4917 - Remove O(n) queries in m2m updates
orf Apr 24, 2017
54bb984
Update relations.py
orf Apr 24, 2017
1d990ea
Update relations.py
orf Apr 24, 2017
1538f53
Update relations.py
orf Apr 24, 2017
ecf8c6f
Update relations.py
orf Apr 24, 2017
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17 changes: 13 additions & 4 deletions rest_framework/relations.py
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Original file line number Diff line number Diff line change
Expand Up @@ -492,10 +492,19 @@ def to_internal_value(self, data):
if not self.allow_empty and len(data) == 0:
self.fail('empty')

return [
self.child_relation.to_internal_value(item)
for item in data
]
if isinstance(self.child_relation, PrimaryKeyRelatedField):
values = list(self.child_relation.get_queryset().filter(pk__in=data))
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Why not use values_list('pk', flat=True) here to just fetch the ids and skip object instantiation?

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@orf orf Apr 25, 2017 •
edited
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Because we then return the values below (line 507), which need to be full model instances.

missing_primary_keys = set(v.pk for v in values) - set(data)
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@EmreSoner EmreSoner Apr 25, 2017 •
edited
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If you use set for unique list, why not use distinct on values filter?

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We are not bothered about distinct values, Model.objects.filter(pk__in=[1, 1]) will only return 1 model AFAIK. We use set() here to just easily find any differences between the returned list of primary keys and the given list of primary keys.


if missing_primary_keys:
self.fail('missing_ids', ids_not_found=list(missing_primary_keys))
else:
values = [
self.child_relation.to_internal_value(item)
for item in data
]

return values

def get_attribute(self, instance):
# Can't have any relationships if not created
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