Cartridge Sale update mysql problem

[Luke Miller]

Greetings,

When creating a Sale object in the mezzanine admin, I get:

OperationalError at /admin/shop/sale/3/
(1093, "You can't specify target table 'shop_product' for update in
FROM clause")

In cartridge/shop/models.py in Sale.save around line 731 (your version
may vary).
priced_objects.filter(**extra_filter).update(**update)

Tthere is a known limitation with mysql that won't let you use the
same table for both the subquery FROM clause and the update target.
http://dev.mysql.com/doc/refman/5.0/en/subquery-errors.html

My hack solution is to "downgrade" that line from an update to a slow
loop through and save when encountering the mysql error, but a much
better solution would be to rewrite the SQL update command to work in
mysql too.

diff -r a68623abf7a5 cartridge/shop/models.py
--- a/cartridge/shop/models.py Fri Sep 16 14:52:32 2011 +1000
+++ b/cartridge/shop/models.py Mon Sep 19 12:33:30 2011 +1000
@@ -10,6 +10,7 @@
from django.db.models.signals import post_save
from django.dispatch import receiver
from django.utils.translation import ugettext_lazy as _
+from _mysql_exceptions import OperationalError

from countries.models import Country

@@ -729,6 +730,13 @@
"sale_to": self.valid_to,
"sale_from": self.valid_from}
priced_objects.filter(**extra_filter).update(**update)
+ except OperationalError: #work around for mysql
+ try:
+ for priced_object in
priced_objects.filter(**extra_filter):
+ priced_object.__dict__.update(**update)
+ priced_object.save()
+ except Warning:
+ pass
except Warning:
pass

[Stephen McDonald]

Thanks Luke - if you'd like to commit a fix for this I'll merge it in. Might need a check around the import as well in case the mysql libs aren't installed (eg for people using postgres)

--
Stephen McDonald

http://jupo.org