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From Ryan King <r...@twitter.com>
Subject Re: atomic test-or-set
Date Tue, 05 Oct 2010 15:30:58 GMT
On Tue, Oct 5, 2010 at 8:23 AM, Ian Rogers <ian.rogers@contactclean.com> wrote:
>
> Does Cassandra have an atomic test-or-set operation?
>
> That is, I want to check to see if a key has a value and, if not, set it to
> something.  But it must be an atomic operation - I can't do a separate fetch
> and then set from the application as that creates a possible race condition
> with another application.
>
> Equivalent to the SQL "update foo set grum = 'bang' where isnull(grum) ..."

You can (sorta) do this per-row, but you can't scan a whole CF and do this.

> Any thoughts how to do this?

I think you can probably do what you want with cassandra, but your
example is too vague to be sure.

-ryan

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