I'm upgrading one of our tools from Python 2.6.4 (SQLAlchemy 0.9.2) to
Python 3.4.1 (SQLAlchemy 1.1.4), and hitting an error when accessing a
PickleType column in one of the ORM classes. This is on MS SQL Server
2012, connecting with pyodbc, and client code running on Windows 8.1 64-bit.
This ORM class is for storing binary image data. The column in question is
set to PickleType, with no constructor arguments like this:
sqlalchemy.Column( 'image_data', sqlalchemy.PickleType )
This turns into an "image" column type on the MS SQL server. For a long
time the Python 2.6 tool has populated objects with that column using code
like this:
self.image_data = open( image_filename, 'rb' ).read( )
Then pulled those images back out to files like this:
image_file = open( image_filename, 'wb' ).write( self.image_data )
Since the upgrade that last "write" line throws a UnicodeDecodeError, on
line 1478 of sqltypes.py, when it calls loads(value). Stack trace pasted
below.
It appears the "loads" call needs to use encoding='bytes' for it to
succeed, but I'm not sure why or how to set it up to do that. Is there a
configuration parameter I'm missing?
I thought this might require using PickleType(protocol=2), but that made no
difference. That column is set up as deferred, but disabling that hits the
same error.
Any suggestions appreciated.
- Adam
 File "d:\projects\ctg\python3\ctg\src\tools\vm_client\vm_client.pyw",
line 1357, in
app.MainLoop( )
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\wx\core.py",
line 1893, in MainLoop
rv = wx.PyApp.MainLoop(self)
 File
"d:\projects\ctg\python3\ctg\src\tools\vm_client\vmlib\views\entries.py",
line 156, in on_item_selected
self.parent.manager.callback_manager.call( vmlib.CB_LOAD_SCREENSHOTS, [
entry ] )
 File
"d:\projects\ctg\python3\ctg\src\tools\vm_client\vmlib\core\callback.py",
line 31, in call
function( *args, **kwargs )
 File
"d:\projects\ctg\python3\ctg\src\tools\vm_client\vmlib\views\screenshot.py",
line 926, in load_screenshots
ss.save_image( img_filename )
 File
"d:\projects\ctg\python3\ctg\src\tools\vm_client\vmlib\core\database.py",
line 471, in save_image
image_file = open( image_filename, 'wb' ).write( self.image_data )
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\attributes.py",
line 237, in __get__
return self.impl.get(instance_state(instance), dict_)
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\attributes.py",
line 584, in get
value = self.callable_(state, passive)
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\strategies.py",
line 305, in _load_for_state
only_load_props=group, refresh_state=state) is None:
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\loading.py",
line 223, in load_on_ident
return q.one()
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\query.py",
line 2756, in one
ret = self.one_or_none()
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\query.py",
line 2726, in one_or_none
ret = list(self)
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\loading.py",
line 75, in instances
rows = [proc(row) for row in fetch]
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\loading.py",
line 75, in
rows = [proc(row) for row in fetch]
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\loading.py",
line 437, in _instance
loaded_instance, populate_existing, populators)
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\orm\loading.py",
line 498, in _populate_full
dict_[key] = getter(row)
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\engine\result.py",
line 93, in __getitem__
return processor(self._row[index])
File
"d:\projects\ctg\python3\ctg\publish\python\lib\site-packages\sqlalchemy\sql\sqltypes.py",
line 1478, in process
return loads(value)
builtins.UnicodeDecodeError: 'ascii' codec can't decode byte 0xff in
position 0: ordinal not in range(128)
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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