my prior experience: - find_or_create does not work - rescuing RecordNotUnique - can deadlock mysql - behaves differently across mysql and postgres transaction semantics so you still need db-specific code e.g. savepoints
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Yup, which is really the best you can do unless you're willing to change your application logic. Repeatable read isolation level (serializable on non-pg) + find_or_create_by is what folks want, but that requires being ready to handle serialization failures
You can also have a delete run after your select but before the data is displayed to the user. That one's even worse since you can't really detect it. Have to just be able to handle concurrent deletes or be willing to ignore it, no way around it
