On Mon, Apr 5, 2010 at 1:46 PM, Paul Prescod <paul@ayogo.com> wrote:
On Mon, Apr 5, 2010 at 1:35 PM, Mike Malone <mike@simplegeo.com> wrote:
>> That's useful information Mike. I am a bit curious about what the most
>> common use cases are for atomic increment/decrement. I'm familiar with
>> atomic add as a sort of locking mechanism.
>
> They're useful for caching denormalized counts of things. Especially things
> that change rapidly. Instead of invalidating the counter whenever an event
> occurs that would incr/decr the counter, you can incr/decr the cached count
> too.

Do you think that a future cassandra increment/decrement would be
incompatible with those use cases?

It seems to me that in that use case, an eventually consistent counter
is as useful as any other eventually consistent datum.
 
An eventually consistent count operation in Cassandra would be great, and it would satisfy all of the use cases I would typically use counts for in memcached. It's just a matter of reconciling inconsistencies with a more sophisticated operation than "latest write wins" (specifically, the reconciliation operation should apply all incr/decr ops).

Mike