Friday, October 26, 2012
On Wednesday, 24 October 2012 18:26:15 UTC-4, Filipe Giusti wrote:
Hi fellow programmers,I was looking for how to keep integrity in some financial transactions and I saw this "This could even happen if you use transactions with the 'serializable' isolation level." in the uniqueness page http://api.rubyonrails.org/classes/ActiveRecord/ . How this is possible with the serializablo isolation level? Aren't the select and update done in the same transaction?Validations/ClassMethods.html# method-i-validates_uniqueness_ of
They are, but that doesn't prevent races like the one in the documentation from occurring - in that case, both transactions find no conflicting records and create a row.
As noted in the docs, if you really really need data consistency you're better off using a unique index and catching ActiveRecord::RecordNotUnique.
--Matt Jones
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