Begin forwarded message:
> From: Ludvig Ericson <lud...@lericson.se>
> Date: February 22, 2009 22:37:16 GMT+01:00
> To: django-developers@googlegroups.com
> Subject: FileField.delete_file opening a file when deleting
>
> django.db.models.fields.files.FileField.delete_file often actually
> winds up opening a file... to close it.
>
> I find this an "interesting" property - as it causes excessive
> request processing when using something like Amazon S3 for the
> storage backend.
>
> Here's the relevant part of a traceback I managed to get, so you can
> see which path the code takes.
>
> File "foobar/models.py", line 88, in switch_quux
> field.delete_file(instance=old, sender=old)
> File "django/db/models/fields/files.py", line 179, in delete_file
> file.close()
> File "django/core/files/base.py", line 147, in close
> self.file.close()
> File "/Users/ludvigericson/Library/Python/django/db/models/fields/
> files.py", line 43, in _get_file
> self._file = self.storage.open(self.name, 'rb')
> File "/Users/ludvigericson/Library/Python/django/core/files/
> storage.py", line 29, in open
> file = self._open(name, mode)
>
> The reason it's reopened is that self.file.close triggers the
> property's _get_file function, which conveniently opens the file if
> it's not already opened.
>
> What puzzles me is how self.file can trigger the descriptor.
> Python's descriptors only trigger when you do `C.x`, not `a = C.x ;
> years later ; a.z`. self.file should be referring not to some proxy,
> but to the actual file object. But I might be confused.
>
> Anyway, would people agree that this is a bug, or at least a
> misfeature? I would really love avoiding this.
>
> I could also add that this particular case only arises if the file
> is multiply referenced, or the default. At the top we see line 179:
>
> 174 if file and file.name != self.default and \
> 175 not sender._default_manager.filter(**{self.name:
> file.name}):
> 176 file.delete(save=False)
> 177 elif file:
> 178 # Otherwise, just close the file, so it doesn't tie up
> resources.
> 179 file.close(
>
> - Ludvig Ericson <lud...@lericson.se>
>
- Ludvig
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