The former.
On 11/19/10 7:31 AM, Chen Xinli wrote:
> 查询是完全基于当天计算的数据吗 还是基于当天和历史数据的合并？
>
> Nanheng Wu <nanhen...@gmail.com>编写：
>
>
> Hi,
>
> Our team decided to use Cassandra as storage solution to a dataset.
> I am very new to the NoSQL world and Cassandra so I am hoping to get
> some help from the community: The dataset is pretty simple, we have
> for each key a number of columns with values. Each day we compute a
> new version of this dataset, the new version will mostly update
> existing keys but could also add and delete some keys. (And we'll
> build a service that queries Cassandra). A key requirement for us is
> we want to keep versions of the dataset and keep N versions around,
> this is in case we discover problems in the current version and need
> to "roll up" to an older one. I thought about creating a Column Family
> per version, this means we will create a new column family every day
> and occasionally delete column families according to some truncation
> policy. I know Cassandra 0.7 now makes changing schema easier, but is
> this a good way to go? I would really like to hear what you guys think
> is the better way to handle this. Thank you.
>
> Best,
> Alex
