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From Jesse McConnell <>
Subject Re: Limit on number of columns
Date Wed, 24 Mar 2010 22:09:22 GMT

"Cassandra's compaction code currently deserializes an entire row (per
columnfamily) at a time. So all the data from a given columnfamily/key
pair must fit in memory. Fixing this is relatively easy since columns
are stored in-order on disk so there is really no reason you have to
deserialize row-at-a-time except that that is easier with the current
encapsulation of functionality. This will be fixed in"

so yes, based on the amount of data you have in there and your memory
allocated to cassandra there is a limit currently...hopefully gone in

I will note that another issue I run across with this is that
get_count will not return within the rpc timeout after you get a
certain amount of columns in there.


jesse mcconnell

On Wed, Mar 24, 2010 at 17:05, Davis, Jeremy <> wrote:
> Hello,
> Is there a practical limit on the number of columns I put on a key?
> Obviously if I tried to grab the entire row at once I would have a problem.
> However, if I had an open ended row, with column names of “1” to “999999999”
> etc. And I only accessed ranges, would there be a practical limit I would be
> running up against? Performance degradation over time, etc?
> I’m running a little micro benchmark to see how well this works, but just
> curious if anyone has any insights.
> Many Thanks,
> -JD

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