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From Kevin Irwig <kevinir...@yahoo.com>
Subject Re: atomicity
Date Sun, 19 Dec 2010 13:18:24 GMT
Thanks a lot, Peter.
K.



----- Original Message ----
From: Peter Schuller <peter.schuller@infidyne.com>
To: user@cassandra.apache.org
Sent: Mon, 20 December, 2010 12:05:17 AM
Subject: Re: atomicity

> Say I have two processes on separate machines, and a Cassandra cluster over
> several machines. If the first process writes (insert) to a column while the
> second process reads (get / get_slice / get_range_slices / others?) from that
> column (say the consistency level is QUORUM if that makes a difference), is 
the
> write "atomic", or could the second process get corrupt (half-written) data?
> What if Cassandra is not a cluster, but runs on a single machine? I'm 
currently
> using version 0.6.3, but the question is general.

You will never see an "in-between" value of a single column. You'd
either see the old value or the new value.

However, given a batch mutation will multiple changes in it your
readers may see the results of said batch mutation being partially
applied; so there is no snapshot consistency type semantics with
respect to multiple values in a batch mutation.

-- 
/ Peter Schuller



      

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