[egenix-users] Two bugs in mxODBC: storing empty string and unicode string

[M.-A. Lemburg]

On 2007-08-13 11:38, Harri Pesonen wrote:
> We are currently using version 2 of mxODBC, but there are a couple of problems:
>  
> 1) Empty string "" is converted to maximum length string (varchar(8000) or
> nvarchar(4000)) when data is stored into database.

mxODBC itself does not do any such conversion. It is possible, however,
that the ODBC driver you are using applies such an conversion.

Note that on SQL Server char columns are padded with spaces up to the
size given in the column definition. This should happen with varchar
columns.

> 2) Unicode string u"abc" is converted to u"abc   ", so that there are equal
> number of extra spaces in the end, when data is stored into database.
>  
> We are using SQL Server 2005 and Python 2.4.4 (and Windows XP). Both of these
> problems must be worked around somehow, but the solution is not easy.
>  
> 1) We use string with 1 character (space) or None (NULL). The problem is because
> there is no such datatype as char(0). varchar(0) would work.
> 2) Workaround not yet found. Except not to use unicode. It is clear that mxODBC
> calculates first the number of bytes, and then uses that as number of
> characters, which is twice too much.
>  
> I don't know if these problems are fixed in the latest release, mxODBC 3.

We'll send you an eval license so that you can check this.

Please note that you should always try to use the latest available ODBC
driver for SQL Server. Because mxODBC uses SQL type binding mode
whenever possible to achieve best possible performance (the ODBC tells
mxODBC which data type to use), the quality of the ODBC matters a lot.

You can also force Python type binding mode by setting

connection.bindmethod = mx.ODBC.Windows.BIND_USING_PYTHONTYPE

The Python type then determines how mxODBC interfaces data to the
ODBC driver.

-- 
Marc-Andre Lemburg
eGenix.com

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