So I figured out that I can do this:
try:
self.session.delete(row)
self.session.flush()
except sqlalchemy.exc.IntegrityError:
print "Can't do that!"
But that really isn't a lot of help, because I'm now stuck with a useless
transaction. If the user makes a bunch of changes, then tries to delete
something that's still being referenced elsewhere, I have to rollback()
*everything* they've done so far. Not good.
So I either need a way to rollback *just* the dodgy deletion, or a way to
anticipate the IntegrityError and not do the deletion at all. The latter would
be better, but I'm OK with either..
Cheers,
Cam
Cameron Jackson
Engineering Intern
Air Operations
Thales Australia
Thales Australia Centre, WTC Northbank Wharf, Concourse Level,
Siddeley Street, Melbourne, VIC 3005, Australia
Tel: +61 3 8630 4591
cameron.jack...@thalesgroup.com.au<mailto:cameron.jack...@thalesgroup.com.au> |
www.thalesgroup.com.au<http://www.thalesgroup.com.au>
From: sqlalchemy@googlegroups.com [mailto:sqlalchemy@googlegroups.com] On
Behalf Of Jackson, Cameron
Sent: Monday, 23 January 2012 11:51 AM
To: sqlalchemy@googlegroups.com
Subject: [sqlalchemy] Anticipating an IntegrityError before it happens (or
noticing it immediately after)
I have a certain ORM model that is being referenced from several other models.
I don't want the user to be able to delete rows from that table that are still
being referenced elsewhere.
Ideally I would like something like:
refs = get_references(row)
if refs:
print "Can't delete row because of:"
for ref in refs:
print ref
else:
self.session.delete(row)
Or even just:
if is_being_referenced(row):
print "You can't delete that!"
else:
self.session.delete(row)
If there's no way to do either of those, then I would settle for:
try:
self.session.delete(row)
except sql.exc.DeletionError:
print "You can't delete that!"
#Again, a way to get a list of the offending references would be nice!
I tried doing the above, catching IntegrityError, but the problem is that SQLA
doesn't 'notice' the error and tell me about it until another action occurs
that causes other queries to be run. Is there some way I can make SQLA check
the integrity of the database immediately after the deletion? Preferably
without running unnecessary queries if that's going to cause a performance hit.
Cheers,
Cam
Cameron Jackson
Engineering Intern
Air Operations
Thales Australia
Thales Australia Centre, WTC Northbank Wharf, Concourse Level,
Siddeley Street, Melbourne, VIC 3005, Australia
Tel: +61 3 8630 4591
cameron.jack...@thalesgroup.com.au<mailto:cameron.jack...@thalesgroup.com.au> |
www.thalesgroup.com.au<http://www.thalesgroup.com.au>
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