diff options
Diffstat (limited to 'django/forms')
| -rw-r--r-- | django/forms/models.py | 26 | ||||
| -rw-r--r-- | django/forms/widgets.py | 6 |
2 files changed, 24 insertions, 8 deletions
diff --git a/django/forms/models.py b/django/forms/models.py index 9686baa6f2..c04a806caa 100644 --- a/django/forms/models.py +++ b/django/forms/models.py @@ -3,6 +3,7 @@ Helper functions for creating Form classes from Django models and database field objects. """ +from collections import deque from itertools import chain from django.core.exceptions import ( @@ -1438,17 +1439,20 @@ class ModelChoiceIterator(BaseChoiceIterator): def __init__(self, field): self.field = field self.queryset = field.queryset + self._deque = deque() + self._generator = self.generator() - def __iter__(self): + def generator(self): if self.field.empty_label is not None: yield ("", self.field.empty_label) - queryset = self.queryset - # Can't use iterator() when queryset uses prefetch_related() - if not queryset._prefetch_related_lookups: - queryset = queryset.iterator() - for obj in queryset: + for obj in self.queryset.iterator(chunk_size=100): yield self.choice(obj) + def __iter__(self): + yield from chain(self._deque, self._generator) + self._deque = deque() + self._generator = self.generator() + def __len__(self): # count() adds a query but uses less memory since the QuerySet results # won't be cached. In most cases, the choices will only be iterated on, @@ -1456,7 +1460,9 @@ class ModelChoiceIterator(BaseChoiceIterator): return self.queryset.count() + (1 if self.field.empty_label is not None else 0) def __bool__(self): - return self.field.empty_label is not None or self.queryset.exists() + return ( + self.field.empty_label is not None or self._deque or self.queryset.exists() + ) def choice(self, obj): return ( @@ -1464,6 +1470,12 @@ class ModelChoiceIterator(BaseChoiceIterator): self.field.label_from_instance(obj), ) + def peek(self): + value = next(self._generator, None) + if value is not None: + self._deque.append(value) + return value + class ModelChoiceField(ChoiceField): """A ChoiceField whose choices are a model QuerySet.""" diff --git a/django/forms/widgets.py b/django/forms/widgets.py index 1bcfeba288..82685a3fea 100644 --- a/django/forms/widgets.py +++ b/django/forms/widgets.py @@ -851,7 +851,11 @@ class Select(ChoiceWidget): if self.allow_multiple_selected: return use_required_attribute - first_choice = next(iter(self.choices), None) + first_choice = ( + self.choices.peek() + if hasattr(self.choices, "peek") + else next(iter(self.choices), None) + ) return ( use_required_attribute and first_choice is not None |