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From Gary Dusbabek <gdusba...@gmail.com>
Subject Re: Cassandra newbie question
Date Mon, 11 Oct 2010 13:02:50 GMT
On Mon, Oct 11, 2010 at 04:01, Arijit Mukherjee <arijit72@gmail.com> wrote:
> Hi All
>
> I've just started reading about Cassandra and writing simple tests
> using Cassandra 0.6.5 to see if we can use it for our product.
>
> I have a data store with a set of columns, like C1, C2, C3, and C4,
> but the columns aren't mandatory. For example, there can be a list of
> (k.v) pairs with only C1 and C2, but no C3 and C4. At the same time,
> there can be a set of records with all the columns present. It's
> possible to consider them as three sets A (with all columns), B (with
> C1 and C2) and C (with C3 and C4). And I'm trying to find out the
> following:
>
> 1. A - B (all records who don't have C3 and C4) and A - C (all record
> who don't have C1 and C2)
> 2. records for whom C2 != C4
>
> It's possible to pick all records and do this processing in my client
> code - but that won't perform well. Is there any way to do these
> within Cassandra? For example, by passing a list of column names so
> that cassandra returns the records with only those columns?

multiget_slice with the SlicePredicate specified using column_names
can do the lookups.  As far as doing the set operations: no, Cassandra
doesn't have the ability to do this server-side.

Gary.


>
> Regards
> Arijit
>

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