#31295: Avoid Select widget triggering additional query in ModelChoiceIterator.
-------------------------------------+-------------------------------------
Reporter: Aurélien Pardon | Owner: nobody
Type: | Status: closed
Cleanup/optimization |
Component: Forms | Version: 2.2
Severity: Normal | Resolution: needsinfo
Keywords: Model | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Carlton Gibson):
* stage: Unreviewed => Accepted
Comment:
Hi Aurélien,
> Maybe there's a way of performing that Select.use_required_attribute()
check without fetching the first item...?
It strikes me that we might be able to do this. This patch passes the
existing tests:
{{{
diff --git a/django/forms/widgets.py b/django/forms/widgets.py
index 40ac1d3162..5bc040065a 100644
--- a/django/forms/widgets.py
+++ b/django/forms/widgets.py
@@ -696,7 +696,16 @@ class Select(ChoiceWidget):
if self.allow_multiple_selected:
return use_required_attribute
- first_choice = next(iter(self.choices), None)
+ iterator = iter(self.choices)
+ # Avoid an extra query if we have a ModelChoiceIterator.
+ try:
+ empty_label = iterator.field.empty_label
+ except AttributeError:
+ pass
+ else:
+ if empty_label is not None:
+ return use_required_attribute
+ first_choice = next(iterator, None)
return use_required_attribute and first_choice is not None and
self._choice_has_empty_value(first_choice)
}}}
So with a further test asserting number of queries, a think about any edge
cases, and a tidy up, I think we can evaluate a patch on that basis.
Thanks for your input!
--
Ticket URL: <https://code.djangoproject.com/ticket/31295#comment:10>
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