#27188: Allow using unique=True with FileField
-------------------------------------+-------------------------------------
Reporter: Jon Ribbens | Owner: Michael
| Scott
Type: New feature | Status: assigned
Component: File | Version: 1.10
uploads/storage |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Comment (by Michael Scott):
I did a little testing over the weekend on the behaviour of FileField's
after the patch has been applied. In general things behaved as you would
expect them to, when unique is set to True then it doesn't allow you to
save more than one instance of the model when a duplicate file name is
used for the FileField field.
However there is a bit of unexpected behaviour when using unique
FileField's across separate models. If the same directory is used, which
by default is the MEDIA_ROOT setting, to store the files from the multiple
models, then the unique constraint may have no effect. This is because
when the (default) storage object saves the file, it checks if the
destination directory already contains a file with the specified name, and
if so it generates a unique file name instead (appends a unique suffix to
the end). In this case that generated file name is what's stored in the
database and therefore as the generated file name is unique the constraint
has no effect.
For example, with models ModelFoo and ModelBar, each having a FileField
with unique set to True. If saving an instance of ModelFoo with file name
"example.txt", the first time will succeed, then if trying to save another
instance of ModelFoo with the same file, the second time will fail as
expected because the table already has a entry in it with that file name.
However if then saving an instance of ModelBar with the same name, then
the storage object generates a unique file name such as
"example_abfgr.txt" as "example.txt" already exists in the directory, and
saves the ModelBar instance with that name. Then when saving another
instance of ModelBar with the same file, the same thing happens again,
meaning the unique constraint has no effect.
I hope this all makes sense. Is the above behaviour something we need to
worry about?
--
Ticket URL: <https://code.djangoproject.com/ticket/27188#comment:4>
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