Like Edward says Cassandra's conflict resolution strategy is LWW (last write wins). This may seem simplistic, but Cassandra's Big Query-esque data model makes it less of an issue than in a pure key/value-store like Riak, for example. When all you have is an opaque value for a key you want to be able to do things like keeping conflicting writes so that you can resolve them later. Since Cassandra's rows aren't opaque, but more like a sorted map LWW is almost always enough. With Cassandra you can add new columns/cells to a row from multiple clients without having to worry about conflicts. It's only when multiple clients write to the same column/cell that there is an issue, but in that case you usually can (and you probably should) model your way around that.

T#


On Fri, Jun 7, 2013 at 4:51 PM, Edward Capriolo <edlinuxguru@gmail.com> wrote:
Conflicts are managed at the column level.
1) If two columns have the same name the column with the highest timestamp wins. 
2) If two columns have the same column name and the same timestamp the value of the column is compared and the highest* wins.

Someone correct me if I am wrong about the *. I know the algorithm is deterministic, I do not remember if it is highest or lowest.


On Thu, Jun 6, 2013 at 6:25 PM, Emalayan Vairavanathan <svemalayan@yahoo.com> wrote:
I tried google and found conflicting answers. Thats why wanted to double check with user forum. 

Thanks


From: Bryan Talbot <btalbot@aeriagames.com>
To: user@cassandra.apache.org; Emalayan Vairavanathan <svemalayan@yahoo.com>
Sent: Thursday, 6 June 2013 3:19 PM
Subject: Re: [Cassandra] Conflict resolution in Cassandra

For generic questions like this, google is your friend: http://lmgtfy.com/?q=cassandra+conflict+resolution

-Bryan


On Thu, Jun 6, 2013 at 11:23 AM, Emalayan Vairavanathan <svemalayan@yahoo.com> wrote:
Hi All,

Can someone tell me about the conflict resolution mechanisms provided by Cassandra?

More specifically does Cassandra provides a way to define application specific conflict resolution mechanisms (per row basis  / column basis)? 
           or 
Does it automatically manage the conflicts based on some synchronization algorithms ?


Thank you
Emalayan