incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From AJ ...@dude.podzone.net>
Subject Re: Atomicity Strategies
Date Wed, 22 Jun 2011 21:42:04 GMT
On 4/9/2011 7:52 PM, aaron morton wrote:
> My understanding of what they did with locking (based on the examples) 
> was to achieve a level of transaction isolation 
> http://en.wikipedia.org/wiki/Isolation_(database_systems) 
> <http://en.wikipedia.org/wiki/Isolation_%28database_systems%29>
>
> I think the issue here is more about atomicity 
> http://wiki.apache.org/cassandra/FAQ#batch_mutate_atomic
>
> We cannot guarantee that all or none of the mutations in your batch 
> are completed. There is some work in this area though 
> https://issues.apache.org/jira/browse/CASSANDRA-1684
>

Just to be clear, you are speaking in the general sense, right?  The 
batch mutate link you provide says that in the case that ALL the mutates 
of the batch are for the SAME key (row), then the whole batch is atomic:

     "As a special case, mutations against a single key are atomic but 
not isolated."

So, is it true that if I want to update multiple columns for one key, 
then it will be an all or nothing update for the whole batch if using 
batch update?  But, if your batch mutate containts mutates for more than 
one key, then all the updates for one key will be atomic, followed by 
all the updates for the next key will be atomic, and so on.  Correct?

Thanks!


Mime
View raw message