On Jan 18, 2008 10:51 AM, Robert Swerdlow <[EMAIL PROTECTED]> wrote:
> I posted this note at comp.lang.python and the response there was that
> this all works outside of Django. What is the problem with using MySQL
> OperationalErrors with Django?
>
> ---------
> In our database code (we are using django v0.96) we wanted to catch
> and handle MySQL OperationalErrors. We use both the Django models and
> database connections.
>
> However, even though we confirmed that a
> _mysql_exceptions.OperationalError are raised (particularly 1213
> deadlock), we cannot catch them with try/except.
>
> Here's the code that did not work:
>
> import _mysql_exceptions
> from _mysql_exceptions import OperationalError
>
> try:
> database_code()
> except (_mysql_exceptions.OperationalError, OperationalError), e:
> error_handling()
>
> Originally, we just had one import, but tried both to ensure that was
> not the problem. In debugging, we confirmed that both type(e) and
> e.__class_ were <class _mysql_exceptions.OperationalError>.
>
> The only work-around we found was:
>
> try:
> database_code()
> except Exception, e:
> if e.__class__.__name__.find('OperationalError') != -1:
> error_handling()
> else:
> raise
>
> This seems silly. If we used any other exception, the except clause
> seems to work correctly.
>
> Is there a problem with _mysql_exceptions.OperationalError? Is there
> a better work-around?
> -----------
>
I cannot recreate any problem with catching OperationalErrors using Django
0.96.1. To test I added a field to a model definition that doesn't exist in
the database and tried a get -- this generates an OperationalError, which I
was able to catch:
Python 2.5.1 (r251:54863, Apr 18 2007, 08:51:08) [MSC v.1310 32 bit (Intel)]
on win32
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from mini.models import Authors
>>> import _mysql_exceptions
>>> def tryget():
... try:
... a = Authors.objects.get(pk=22)
... except _mysql_exceptions.OperationalError, e:
... print 'get failed with OperationalError: ' + str(e)
... return
... print 'get succeeded, a = ' + str(a)
...
>>> tryget()
get failed with OperationalError: (1054, "Unknown column 'mini_authors.Xtra'
in 'field list'")
>>> import django
>>> django.VERSION
(0, 96.099999999999994, None)
>>>
My MySQLdb is version 1.2.2.
I don't know why a 1213 OperationalError would be treated any differently
than the 1054 one above.
It sounds very odd to me that you verified the class of the exception you
catch with 'catch Exception, e' is <class
_mysql_exceptions.OperationalError> but you cannot 'catch
_mysql_exceptions.OperationalError'.
Sorry, but I have no explanation for how that could happen....all I can say
is catching OperationalErrors when running Django code works for me.
Karen
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