mapper _postfetch error regarding data conversion

[Former user]

Try this:

from sqlalchemy import *
engine = create_engine('sqlite://filename=:memory:', encoding='latin2')

test = Table('test', engine, 
    Column('id',  Integer, primary_key=True),
    Column('txt', Unicode(50)))
test.create()
class Test(object):
    pass
assign_mapper(Test, test)

txt = u"\u0160\u0110\u0106\u010c\u017d"
t1 = Test(id=1, txt = txt)
assert t1.txt == txt

objectstore.commit() # this will raise exception at mapper.py(654)

You will get:

File "...\sqlalchemy\mapping\mapper.py", line 654, in _postfetch
  if self._getattrbycolumn(obj, c) != params[c.name](c.name):
UnicodeDecodeError: 'ascii' codec can't decode byte 0xa9 in position 0: ordinal not in range(128)

_postfetch fails because _getattrbycolumn returns unicode and params[c.name](c.name) contains converted value.

I guess that not only unicode suffers from this line of code. This line is comparing original value (unicode) with converted values which is prepared for database.

[Former user]

I did the following as a temporary workaround:

Index: lib/sqlalchemy/mapping/mapper.py
===================================================================
--- lib/sqlalchemy/mapping/mapper.py    (revision 1126)
+++ lib/sqlalchemy/mapping/mapper.py    (working copy)
@@ -651,8 +651,9 @@
             for c in table.c:
                 if c.primary_key or not params.has_key(c.name):
                     continue
-                if self._getattrbycolumn(obj, c) != params[c.name](c.name):
-                    self._setattrbycolumn(obj, c, params[c.name](c.name))
+                val = c.type.convert_result_value(params[c.name](c.name), table.engine)
+                if self._getattrbycolumn(obj, c) != val:
+                    self._setattrbycolumn(obj, c, val)

     def delete_obj(self, objects, uow):
         """called by a UnitOfWork object to delete objects, which involves a

It allows for this code to pass:

assert t1.txt == txt
objectstore.commit()
assert t1.txt == txt

But I'm not entirely satisified because this (less-correct code) will fail:

t1 = Test(id=1, txt = txt.encode('latin2'))
assert t1.txt == txt.encode('latin2')
objectstore.commit() # this will again raise exception at mapper.py

Even if it passed, value of t1.txt would be different after commit().

[Mike Bayer]

fixed in changeset:1127