#13758: MySQLdb utf8_bin and django causes UnicodeDecodeError
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Reporter: sam.vev...@gmail.com | Owner:
nobody
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: 1.2
Keywords: utf8_binMySQLdb collation unicode bytestring | Stage:
Unreviewed
Has_patch: 0 |
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Issue:
I have a Model with a FileField. When I delete that instances of that
model that have unicode characters in their filenames, I get a
{{{
'ascii' codec can't decode byte 0xc3 in position 18: ordinal not in
range(128)
}}}
I finally traced the problem back to my database collation: utf8_bin. I
chose utf8_bin so I could order the strings in a case-sensitive manner.
FYI, MySQLdb does not return python unicode strings with a utf8_bin
collation, it returns utf8 bytestrings. for a brief description of that
issue see:
http://code.djangoproject.com/ticket/8340#comment:4
The traceback from my exception reveals the exception being thrown in
"django/db/models/fields/files.py" in get_prep_value (line 248).
FileField is a subclass of Field, but implements the same backend
MySQL type (varchar) as a CharField. However it seems that FileField
and CharField have completely different implementations of
get_prep_db.
Here is CharField's implementation:
def to_python(self, value):
if isinstance(value, basestring) or value is None:
return value
return smart_unicode(value)
def get_prep_value(self, value):
return self.to_python(value)
Here is Filefield's:
def get_prep_value(self, value):
"Returns field's value prepared for saving into a database."
# Need to convert File objects provided via a form to unicode for
database insertion
if value is None:
return None
return unicode(value)
My experimentations revealed that if I replace the FileField
implementation of get_prep_value with CharField's implementation, the
exception
goes away. The issue is that the default encoding is ascii and so
unicode() called on a utf8 byte str blows up. The CharField
implementation simply checks if the value is an instance of basestring
and quietly passes it through.
--
Ticket URL: <http://code.djangoproject.com/ticket/13758>
Django <http://code.djangoproject.com/>
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