On Wednesday, February 19, 2014 8:29:28 PM UTC-8, [email protected]
wrote:
>
> Hi there,
>
> Only after I opened an issue at Github I realized I should have posted
> this here before, sorry about that...
>
> From Sequel documentation re: Model Hooks:
>
> So when a model object is created, you want to add a background job that
> will create the thumbnail for the picture. If you used after_save for this
> and transactions are being used, you are subject to a race condition where
> the background job library will check the database table for the record
> before the transaction that saved the record commits, and it won't be able
> to see the record's data. Using after_commit, you are guaranteed that the
> background job library will not get notified of the record until after the
> transaction commits and the data is viewable.
>
> Unless I'm missing something, there is no built-in way to check if the
> current record was new on an after_commit hook. I have a use case where I
> need to perform a background job only for new records, so in the
> after_save hook I'm setting my own flag based on @was_new.
>
> Here we can see that @was_new is reset just before the after_commit hook
> runs:
>
> https://github.com/jeremyevans/sequel/blob/master/lib/sequel/model/base.rb#L1656-L1665
>
> Could we make @was_new available in the after_commit hook? Or is there
> another to achieve this
>
@was_new cannot be made available in after_commit, because you never know
when after_commit will run:
DB.transaction do
model = Model.create(:a=>1)
model.update(:b=>2)
end
@was_new is a bad idea, and it's my mistake for introducing it. Anyway,
you can do what you want via after_create:
def after_create
super
db.after_commit{...}
end
Were I to do it over again, there wouldn't be model commit/rollback hooks,
you would have to call Database#after_commit/after_rollback in the other
model hooks.
Thanks,
Jeremy
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