unpickling stackunderflow: MySQLdb 1.2.1g3 is returning array instances for BLOB columns

[Former user]

I think the fix is to specialize the PickleType in sqlalchemy.database.mysql based on the version of the driver. I'll try  to rustle up a patch if this ticket isn't declared bogus.

* mysqld 4.1.12-Debian_1ubuntu3.1
* sqlalchemy trunk r1306
* MySQLdb 1.2.1g3
* python 2.4.2 gcc 4.0.2

stacktrace::

    UnpicklingError: unpickling stack underflow
    Traceback:
      File "tables.py", line 266, in ?
        encoding='latin1')
      File "tables.py", line 259, in test_tables
        print row
      File "/home/robin/devel/sqlalchemy/lib/sqlalchemy/engine.py", line 863, in __repr__
        return repr(tuple([key) for key in range(0, len(self.__row))](self.__parent._get_col(self.__row,)))
      File "/home/robin/devel/sqlalchemy/lib/sqlalchemy/engine.py", line 812, in _get_col
        return rec[0](0).engine_impl(self.engine).convert_result_value(row[rec[1](rec[1)], self.engine)
      File "/home/robin/devel/sqlalchemy/lib/sqlalchemy/types.py", line 175, in convert_result_value
        return pickle.loads(str(buf))
    Traceback (most recent call last):
      File "tables.py", line 266, in ?
        encoding='latin1')
      File "tables.py", line 259, in test_tables
        print row
      File "/home/robin/devel/sqlalchemy/lib/sqlalchemy/engine.py", line 863, in __repr__
        return repr(tuple([key) for key in range(0, len(self.__row))](self.__parent._get_col(self.__row,)))
      File "/home/robin/devel/sqlalchemy/lib/sqlalchemy/engine.py", line 812, in _get_col
        return rec[0](0).engine_impl(self.engine).convert_result_value(row[rec[1](rec[1)], self.engine)
      File "/home/robin/devel/sqlalchemy/lib/sqlalchemy/types.py", line 175, in convert_result_value
        return pickle.loads(str(buf))
    cPickle.UnpicklingError: unpickling stack underflow

[Former user]

adds is instance(value, array) check to types.Binary, benign for drivers that do not return blobs as python.array instances

[Mike Bayer]

wouldnt we want to fix the MySQL binary type to return the same kind of data as everything else ?

[Former user]

Thats what I tried initialy. Modified MSBinary and introduced MSPickleType, declared the appropriate mapping from PickleType to MSPickleType, but got bogged down in inhertance / aggregation issues etc. Couldn't get it to work.

I was thinking that for classes like PickleType, and for simple differences in the type of python intrinsic used, it covers more ground to make the less elegant change in one obviouse place. But yes, I aggree, my first instinct was to change MSBinnary as you suggest.

[Mike Bayer]

just dont worry about this one. the types system is totally busted, apparently im going to have to rework it all over again.

[Mike Bayer]

Ok this is fixed for now, unfortunately I had to modify the types system again and break the documented method of creating custom types...(TypeDecorator is back....), in changeset:1356

also you can run the full suite of unittests with mysql now as I qualified the non-passing tests with a decorator.