incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Lucas Nodine <>
Subject Re: Not overwriting values
Date Tue, 21 Sep 2010 12:29:06 GMT
Chris, I believe if the timestamp being written if the same or older it will
not apply the write, but do not quote me on this, test it.  In this case, if
the timestamp value does not matter, you could simply always write with a
timestamp of 1.

- LN

On Tue, Sep 21, 2010 at 5:58 AM, Christian Decker <> wrote:

> Hi all,
> I have a rather strange problem I'd like to address. As I understand it a
> write in cassandra always overwrites already existing data, so it is not
> possible to have a way to create an index pointing to the first entry
> matching some criteria. What I mean is that I have a CF which stores user
> purchases and now I want to find the first time a user bought an item from a
> certain class of objects. For this I was thinking about a CF with SCFs, the
> CF key being the user ID and the SCF key being the class id of the item and
> then the value would be the key of the purchase in the purchases CF.
> Obviously for this to work I'd have to check if a value like
> firstPurchases[123][987] already exists and if not write it, but it there a
> way to implement it without the additional read?
> Regards,
> Chris

Lucas J. Nodine
Assistant Labette County Attorney
201 S. Central, Suite B
Parsons, KS 67357
(620) 421-6370

View raw message