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From Simon Reavely <simon.reav...@gmail.com>
Subject Re: atomic test-or-set
Date Wed, 06 Oct 2010 21:36:06 GMT
Ryan,

Independent of this ambiguous requirement what were you thinking about. What I am trying to
ask is can you be more specific/concrete about when you can

Simon Reavely


On Oct 5, 2010, at 11:30 AM, Ryan King <ryan@twitter.com> wrote:

> 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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