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Date: Wed, 5 Oct 2011 13:17:22 -0500 (CDT)
From: "Konstantin  Naryshkin" <konstantinn@a-bb.net>
To: user@cassandra.apache.org
Subject: Re: Question about sharding of rows and atomicity
Message-ID: <9992f146-987a-4fd5-ad7a-bdd1d588667b@klap>
In-Reply-To: <4E8C9D60.7000109@likewise.com>
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Cassandra does not break apart a row. All of the columns of a row are kept on the same nodes.

I believe that writing multiple columns of the same row is transactional, but not atomic. By which I mean that if one column is written all the other ones will be written as well, but if a read happens while the write is being done it is possible that only some of the columns will have the new values.

----- Original Message -----
From: "Don Smith" <dsmith@likewise.com>
To: user@cassandra.apache.org
Sent: Wednesday, October 5, 2011 2:09:36 PM
Subject: Question about sharding of rows and atomicity

Does Cassandra shard the columns of a single row across multiple nodes 
so that to read the columns of the row it may need access to multiple 
nodes?   I'd say "no."   Will a read from a given node ever return 
partial results or is the write to a node of a row atomic?

  Thanks, Don