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Date: Mon, 9 Aug 2010 19:17:49 +0200
Message-ID: <AANLkTinAfiCpO-9NgG6LAzNjxZXCPotmTMpgGFRfE2MR@mail.gmail.com>
Subject: Re: batch_mutate atomicity
From: Peter Schuller <peter.schuller@infidyne.com>
To: user@cassandra.apache.org
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> I am using the familiar meanings from ACID:
>
> atomic means either the entire update will succeed or none of it.
>
> isolated means other threads will not see partial updates while it is
> being applied.

A related concern is whether there is a write *ordering* guarantee for
mutations within a row key. Ensuring consistency in the face of
concurrent access can in some (probably several) cases become a lot
easier with an ordering guarantee which would otherwise necessitate an
RPC call between potentially every mutation (depending on where
dependencies between writes are).

Upon cursory inspection it *seems* to me that ordering is maintained,
but even if this is correct, can one consider Cassandra to have such
an ordering guarantee or is any such behavior an artifact of current
implementation details?

By ordering guarantee I am only thinking of single column reads or
distinct get_slice() calls; I am not expecting ordering guarantees
w.r.t. visibility within a single get_slice(). (Additionally I am
assuming QUOROM or RF=1, else it would not be useful to rely on
anyway.)

-- 
/ Peter Schuller