model objects can fail during save

[Jack Moffitt <metajack@…>]

Currently django uses an existence test (at least on postgresql_psycopg2 backend, but I assume it does the same thing everywhere) before and INSERT or UPDATE to decide which to do. This can fail if another connection does an INSERT or a DELETE while the existence test is running, even in a transaction block (unless the transaction isolation level is serializable) as each statement can potentially see a different view of the database depending on which transactions have already completed before that statement executes.

I'm not sure how to fix this (serializable transactions are probably not the right answer), and it is probably an edge case for most applications, but I'm entered a bug for it so that people know this issue exists.

[Michael Radziej <mir@…>]

Hmm ... I don't consider it a bug that save() throws an exception, you're supposed to deal with this in your code.

But the documentation should explain it, and generic views should handle it. Perhaps this can be done by re-validating if save() throws a database exception.

We first need to find out what's the best way to take, so I put it into stage "Needs Decision".

[Jacob]

There's no way we can prevent save() from raising an integrity error, so this is wontfix.