[egenix-users] mx.odbc segmentation fault on fetching string
M.-A. Lemburg
mal at egenix.com
Tue Jun 3 18:43:19 CEST 2008
For the other list members and the archives ...
After some private discussion, it turned out that using iODBC instead
of unixODBC solved the problem.
However, we were not able to reproduce the problem on our machines, so
in case you run into similar problems, please let us know.
FWIW, the only difference between our setup and Wouter's was the version
of unixODBC being used - they had 2.2.11 installed, we compile mxODBC against
the more recent 2.2.12.
Note that when using FreeTDS, it is often better to try using iODBC
as well. Our internal tests often show a much better performance of the
FreeTDS driver with iODBC than unixODBC, with much better being up to
2-3x faster depending on the usage pattern, so it's well worth a try.
Thanks.
On 2008-06-03 11:56, M.-A. Lemburg wrote:
> We ran our test suite using our release candidate 2 of mxODBC 3.0.2
> against FreeTDS 0.82 with unixODBC and iODBC, with SQL Server 2000 and
> SQL Server 2005, but could not reproduce the problem you are seeing.
>
> We've uploaded the RC2 to our server. Could you try with that
> version ?
>
> http://downloads.egenix.com/python/egenix-mxodbc-3.0.2_rc2.linux-x86_64-py2.5_ucs4.prebuilt.zip
>
>
> Thanks,
>
> On 2008-06-03 11:35, M.-A. Lemburg wrote:
>> On 2008-06-03 11:20, M.-A. Lemburg wrote:
>>> On 2008-06-03 02:49, Wouter van Atteveldt wrote:
>>>> Dear list,
>>>>
>>>> I am evaluating mx.odbc for connecting to a MS SQL server from my
>>>> Linux machine using freetds 0.82. I can connect and query using isql
>>>> without problem, but I get a segmentation fault if I fetch using the
>>>> mx.odbc interface.
>>>
>>> isql uses a different, all-strings based access method to the ODBC
>>> driver, so it can really only be used to verify that a connection
>>> works, not much more.
>>>
>>> mxODBC always tries to use the best possible access method to
>>> avoid frequent copying and conversion of the data.
>>>
>>>> wva at amcat:~/tmp$ isql -v AmcatDB <UID> <PWD>
>>>> +---------------------------------------+
>>>> | Connected!
>>>> [...]
>>>> +---------------------------------------+
>>>> SQL> select top 1 projectid, name from projects
>>>> [...]
>>>> | 1 | test
>>>> [...]
>>>> SQLRowCount returns 1
>>>> 1 rows fetched
>>>>
>>>> wva at amcat:~/tmp$ python testodbc.py
>>>> connected to Microsoft SQL Server 08.00.2039
>>>> Executed, fetching...
>>>> [(1,)]
>>>> Executed, fetching...
>>>> Segmentation fault
>>>
>>> Could you send us the core dump of this segfault ? It is most likely
>>> a problem in the new FreeTDS ODBC driver. FreeTDS 0.63 works just fine
>>> on x64 machines.
>>
>> ... and so does version 0.64. We're testing 0.82 now. Did you compile
>> FreeTDS against unixODBC or iODBC ?
>>
>>> It would be great if you could also provide the table
>>> definition and example data that allows us reproducing the
>>> error on our servers.
>>>
>>>> wva at amcat:~/tmp$ cat testodbc.py
>>>> import mx.ODBC
>>>> db = mx.ODBC.unixODBC.connect("AmcatDB", "<UID>", "<PWD>")
>>>> print "connected to %s %s" % (db.dbms_name, db.dbms_version)
>>>> c = db.cursor()
>>>> c.executedirect("select top 1 projectid from projects")
>>>> print "Executed, fetching..."
>>>> print c.fetchall()
>>>> c.executedirect("select top 1 projectid, name from projects")
>>>> print "Executed, fetching..."
>>>>
>>>> print c.fetchall()wva at amcat:~/tmp$ uname -a
>>>> Linux amcat 2.6.18-6-amd64 #1 SMP Sun Feb 10 17:50:19 UTC 2008 x86_64
>>>> GNU/Linux
>>>> wva at amcat:~/tmp$ python -c "import
>>>> sys;print(sys.maxunicode<66000)and'UCS2'or'UCS4'"
>>>> UCS4
>>>>
>>>> As you can see, it returns the MS SQL version number so it has some
>>>> contact with the remote db. I installed using
>>>> egenix-mxodbc-3.0.1.linux-x86_64-py2.5_ucs4.prebuilt.zip, which I
>>>> think should be OK as x86_64 == AMD64 (right?). projected is int,
>>>> name is a varchar(255) column, and the table should have a couple
>>>> hundred entries at most.
>>>>
>>>> The relevant etc files:
>>>>
>>>> wva at amcat:~/tmp$ tail -4 /usr/local/freetds/etc/freetds.conf
>>>> [amcatdb]
>>>> host = localhost
>>>> port = 1433
>>>> tds version = 8.0
>>>> wva at amcat:~/tmp$ cat /etc/odbc.ini
>>>> [AmcatDB]
>>>> Driver = FreeTDS
>>>> Description = amcatdb MS SQL Database
>>>> Trace = No
>>>> Servername = amcatdb
>>>> Database = anoko
>>>> wva at amcat:~/tmp$ cat /etc/odbcinst.ini
>>>> [FreeTDS]
>>>> Description = v0.63 with protocol v8.0
>>>> Driver = /usr/local/freetds/lib/libtdsodbc.so
>>>> UsageCount = 1
>>>>
>>>> Note that I am using an SSH tunnel to connect to the sql server,
>>>> hence the localhost. This does not give trouble using either tsql,
>>>> isql, or python-sybase (on a previous install), so I am not
>>>> expecting this to be the cause of the problem.
>>>>
>>>> Any help greatly appreciated!
>>>
>>> Thanks,
>>
>
--
Marc-Andre Lemburg
eGenix.com
Professional Python Services directly from the Source (#1, Jun 03 2008)
>>> Python/Zope Consulting and Support ... http://www.egenix.com/
>>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/
>>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/
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