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From Aaron Morton <aa...@thelastpickle.com>
Subject Re: more questions on Cassandra ACID properties
Date Tue, 20 Jul 2010 21:22:29 GMT
Yes, both inserts (colD and colE) will succeed if you send insert() or batch_mutation()s from
the client.

It's also correct to think of them as insert-or-update calls.

Aaron


On 21 Jul, 2010,at 07:58 AM, Alex Yiu <bigcontentflow@gmail.com> wrote:

>
>
> Hi,
>
> I have more questions on Cassandra ACID properties. 
> Say, I have a row that has 3 columns already: colA, colB and colC
>
> And, if two *concurrent* clients perform a different insert(...) into the same row,
> one insert is for colD and the other insert is for colE. 
> Then, Cassandra would guarantee both columns will be added to the same row.
>
> Is that correct? 
>
> That is, insert(...) of a column does NOT involving reading and rewriting other existing
columns of the same row? 
> That is, we do not face the following situation:
> client X: read colA, colB and colC; then write: colA, colB, colC and colD
> client Y: read colA, colB and colC; then write: colA, colB, colC and colE
>
>
> BTW, it seems to me that insert() API as described in the wiki page: 
> http://wikiapache.org/cassandra/API
> should handle updating an existing column as well by the replacing the existing column
value.
>
> If that is the case, I guess we should change the wording from "insert" to "insert or
update" in the wiki doc
> And, ideally, insert(...) API operation name would be adapted to update_or_insert(...)
>
>
> Looking forward to replies that may confirm my understanding.
> Thanks!
>
>
> Regards,
> Alex Yiu
>
>

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