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From Ritesh Tijoriwala <tijoriwala.rit...@gmail.com>
Subject Re: New Chain for : Does Cassandra use vector clocks
Date Thu, 24 Feb 2011 02:28:21 GMT
I was about to ask what Anthony's latest post below captures - if we don't
have vector clocks and no locking, how does cassandra prevent/detect
conflicts? This is somewhat related to the question I asked in last post -
http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/How-does-Cassandra-handle-failure-during-synchronous-writes-td6055152.html

<http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/How-does-Cassandra-handle-failure-during-synchronous-writes-td6055152.html>
Thanks,
Ritesh



On Wed, Feb 23, 2011 at 6:22 PM, Anthony John <chirayithaj@gmail.com> wrote:

> Apologies : For some reason my response on the original mail keeps bouncing
> back, thus this new one!
> > From the other hand, the same article says:
> > "For conditional writes to work, the condition must be evaluated at all
> update
> > sites before the write can be allowed to succeed."
> >
> > This means, that when doing such an update CL=ALL must be used
>
> Sorry, but I am confused by that entire thread!
>
> Questions:-
> 1. Does Cassandra implement any kind of data locking - at any granularity
> whether it be row/colF/Col ?
> 2. If the answer to 1 above is NO! - how does CL ALL prevent conflicts.
> Concurrent updates on exactly the same piece of data on different nodes can
> still mess each other up, right ?
>
> -JA
>

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