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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: Limit on the size of a list
Date Mon, 13 May 2013 19:43:38 GMT
Whenever I mention the limit in a talk I say, "2 Billion columns" in a faux
10 year old voice :). Cassandra can have a 2billion column row. A 60MB row
in row cache will make the JVM sh*t the bed. (row cache you should not use
anyway). As rcoli points out a 35 GB row, I doubt you can do anything with
it that will finish in less then the rpc_timeout. In a single request I
personally would not try more then 10K columns.


On Mon, May 13, 2013 at 2:08 PM, Robert Coli <rcoli@eventbrite.com> wrote:

> On Sun, May 12, 2013 at 6:26 PM, Edward Capriolo <edlinuxguru@gmail.com>
> wrote:
> > 2 billion is the maximum theoretically limit of columns under a row. It
> is
> > NOT the maximum limit of a CQL collection. The design of CQL collections
> > currently require retrieving the entire collection on read.
>
> Each column has a byte overhead of 15 bytes [1]. Assuming a column key
> of type "int" [2] and no column value, a 2 billion column row is
> approximately 35 gigabytes. This is before including the column index.
> Anyone attempting to actually create and interact with a single row
> containing 2 billion columns seems likely to quickly discover just how
> meaningless the theoretical maximum is, so I'm not sure why we refer
> to this number..
>
> =Rob
> [1]
> http://btoddb-cass-storage.blogspot.com/2011/07/column-overhead-and-sizing-every-column.html
> [2] The minimum size to actually have 2Bn unique column keys.
>

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