On Mon, Sep 6, 2010 at 7:12 PM, Patryk Zawadzki <pat...@pld-linux.org> wrote:
> It would be more useful if you could explicitly
> enter_isolation_block() and leave_isolation_block() as needed
> (currently there is no way to commit the isolating transaction other
> than doing a raw SQL query or accessing psycopg internals).
Another usecase I just came along:
Say I have to generate some unique string for the database. Something like that:
potential = base = slugify(obj.bar)
suffix = 0
while True:
if not Baz.objects.filter(foo=potential).exists():
obj.foo = potential
obj.save()
break
suffix += 1
potential = '%s-%s' % (base, suffix)
Except it's possible that another process or thread commits an
identical object right between the call to exists() and the save().
What I'd really want to do is something closer to this:
potential = base = slugify(obj.bar)
suffix = 0
found = False
while not found:
enter_isolation_block(ISOLATION_SERIALIZABLE)
if not Baz.objects.filter(foo=potential).exists():
obj.foo = potential
obj.save()
found = True
leave_isolation_block()
suffix += 1
potential = '%s-%s' % (base, suffix)
Of course with new python versions we can get the extra sugar coating:
with db.isolation(ISOLATION_SERIALIZABLE):
# ...
--
Patryk Zawadzki
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