id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
25547	refresh_from_db leaves FieldFile with reference to db_instance	vinnyrose	nobody	"#### models.py
{{{#!python
class Product(models.Model):
    myfile = models.FileField(upload_to='folder')
}}}

##### elsewhere.py
{{{#!python
product = Product.objects.create(myfile='filename')
product.refresh_from_db()

assert id(product.myfile.instance) == id(product) # false
}}}

{{{product.file.instance}}} is actually {{{db_instance}}} which is used internally in {{{refresh_from_db}}}.

This leads to strange results when trying to use {{{FieldFile.save}}} or {{{FieldFile.delete}}}, since you would be modifying {{{db_instance}}} instead of the intended {{{instance}}}. This also means any field that uses a {{{descriptor_class}}} that returns an {{{attr_class}}} will have this same issue, I've used this pattern for custom fields.


This could most simply be fixed in the {{{FileDescriptor}}} itself, because frankly I don't see how this could be fixed for all cases in which a field has reference to the {{{instance}}} from which it was instatianted from. Perhaps a warning on {{{refresh_from_db}}} in the docs about this risk?
"	Bug	closed	Database layer (models, ORM)	1.8	Normal	fixed	refresh_from_db, fieldfile		Accepted	1	0	0	0	0	0