id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
5043	Postgresql transaction error handling is different	Nis Jørgensen <nis@…>	nobody	"(Discussion is happening here): http://groups.google.com/group/django-users/browse_thread/thread/8004a40b3c607d08/7b7ed19d276033df

Postgresql does error handling inside transactions differently than mySQL and sqlite. When using the latter two, you can do this inside a transaction:


{{{
class MyModel(Model):
    uniquefield = CharField(max_length=200,unique=True)

MyModel.objects.create(uniquefield='Some non-unique value')
try:
    MyModel.objects.create(uniquefield='Some non-unique value')
except:
    MyModel.objects.create(uniquefield='A unique value')
}}}

while in postgres the last query will fail as well.

Note that postgresql is by default inside a transaction - ticket #3460 is aimed at fixing this.

I believe the solution is to wrap the ""execute"" method to generate savepoints when inside a transaction. Something like  the following (untested) pseudocode:

{{{
def myexecute(self, *args,**kwargs):
    if self.is_in_transaction:
        self.create_save_point(identifier)  
        try: 
            self.execute(*args,**kwargs)
        except DatabaseError,e:
            self.rollback(identifier)
            raise
    else:
        self.execute(*args,**kwargs)

}}}

"		closed	Database layer (models, ORM)	dev		duplicate		metajack@… richard.davies@…	Design decision needed	0	0	0	0	0	0