#32244: ORM inefficiency: ModelFormSet executes a single-object SELECT query per
formset instance when saving/validating
-------------------------------------+-------------------------------------
Reporter: Lushen Wu | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Database layer | Version: 3.1
(models, ORM) |
Severity: Normal | Resolution:
Keywords: formsets | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Lushen Wu):
I figured out a very hacky workaround that preserves the formset
functionality we need. Basically in {{{BookForm}}} you can override
{{{ModelForm._clean_fields()}}}
{{{
def _clean_fields(self):
# remove 'id' field so it's not cleaned
# (this is the ModelChoiceField that's generating an extra SELECT
query per Book object in the formset during clean)
id_field = self.fields.pop('id')
# run normal cleaning, with the form now unaware of its own 'id'
field
super(BookForm, self)._clean_fields()
# add 'id' field back and insert it into clean_data
id_value = id_field.widget.value_from_datadict(self.data,
self.files, self.add_prefix('id'))
self.cleaned_data['id'] = id_value
# add the 'id' field back into the form
self.fields['id'] = id_field
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/32244#comment:6>
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