Hi,
I have two models Source and Input, where Input has an FK to Source like
this:
class Source(db_models.Model):
scheme = db_models.CharField(...)
path = db_models.CharField(...)
display_as = db_models.CharField(...)
class Input(db_models.Model):
name = db_models.CharField(...)
description = db_models.CharField(...)
type = db_models.CharField(...)
source = db_models.ForeignKey(Source, on_delete=db_models.CASCADE)
reuse = db_models.CharField(...)
value = db_models.CharField(...)
The instances of Source are statically created, and number 20 or so in
total. The instances of Input number in the millions, and may be loaded
from external files/network endpoints. When Input instances are created, we
perform normal Django validation processing, involving
form.is_valid()/form.errors. As we know, Django 5.x does something like:
1. Form field validation using Form.clean_xxx().
2. Form cross-field validation using Form.clean().
3. Model validation, including validating the FK.
like this:
...
File "/.../django/forms/forms.py", line 197, in is_valid return
self.is_bound and not self.errors File "/.../django/forms/forms.py", line
192, in errors self.full_clean() File "/.../django/forms/forms.py", line
329, in full_clean self._post_clean() File "/.../django/forms/models.py",
line 496, in _post_clean self.instance.full_clean(exclude=exclude,
validate_unique=False) File "/.../django/db/models/base.py", line 1520, in
full_clean self.clean_fields(exclude=exclude) File
"/.../django/db/models/base.py", line 1572, in clean_fields setattr(self,
f.attname, f.clean(raw_value, self)) File
"/.../django/db/models/fields/__init__.py", line 830, in clean
self.validate(value, model_instance) File
"/.../django/db/models/fields/related.py", line 1093, in validate if not
qs.exists():
...
In one experiment, I observe that this results in 143k queries, taking a
total of 43s. Is there a way to short circuit this Model-level validation?
Since I know the ~20 instances of Source, even a cache of
Source.objects.all() would be a very cheap, but I cannot see any way to
inject that into the code for line 1093:
def validate(self, value, model_instance):
if self.remote_field.parent_link:
return
super().validate(value, model_instance)
if value is None:
return
using = router.db_for_read(self.remote_field.model,
instance=model_instance)
qs = self.remote_field.model._base_manager.using(using).filter(
<<<< queryset created here
**{self.remote_field.field_name: value}
)
qs = qs.complex_filter(self.get_limit_choices_to())
if not qs.exists():
<<<< queryset evaluated here, line 1093
raise exceptions.ValidationError(...)
We actually have several versions of this problem so any ideas are welcome.
Thanks, Shaheed
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