Have you drilled down to `self._create_object_from_params(params)`? It does
handle this case, as follows:
try:
with transaction.atomic(using=self.db):
params = {k: v() if callable(v) else v for k, v in params.items()}
obj = self.create(**params)
return obj, True
except IntegrityError:
exc_info = sys.exc_info()
try:
return self.get(**lookup), False
except self.model.DoesNotExist:
pass
raise exc_info[0](exc_info[1]).with_traceback(exc_info[2])
That said, I do think that doing it in one single atomic query has
advantages (for one, the above is still not atomic, though the failure case
in the end is much less likely). But a complicated postgres-specific query
is perhaps not worth it. If you can think of a generic method, that works
with READ COMMITTED, that would be interesting. Some conditions I would
personally impose are:
1. Should not increment the primary key sequence in the `get` case. This is
not critical for correctness, I just like to avoid these holes :)
2. The `get` case should remain fast. In the current code, `get_or_create`
is the same as `get` when the row already exists. In many (most?) scenarios
this is the 99% case.
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