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From Yang <teddyyyy...@gmail.com>
Subject Re: What does a write lock ?
Date Thu, 07 Jul 2011 19:23:20 GMT
validation is on the new incoming column ,not the old row,right?
 On Jul 7, 2011 8:25 AM, "Jeffrey Kesselman" <jeffpk@gmail.com> wrote:
> Hi Jonnathan,
>
> This brings up an important question. I have been assuming that the
> validation check is part of the atomic update operation. Is this NOT the
> case? Which is to say, can the row be changed between the time the
> validation method is executed and the validated data is written?
>
> The reason I ask is because I have been thinking of this as effectively a
> write-lock on the row during the entire update
> process, including validation, but your answer has caused some concerns
that
> this is wrong...
>
> Thanks
>
> JK
>
> On Thu, Jul 7, 2011 at 2:01 PM, Jonathan Ellis <jbellis@gmail.com> wrote:
>
>> None of the above, it uses a glorified CAS* at the column level
>>
>> *http://en.wikipedia.org/wiki/Compare-and-swap
>>
>> On Thu, Jul 7, 2011 at 12:51 PM, A J <s5alye@gmail.com> wrote:
>> > Does a write lock:
>> > 1. Just the columns in question for the specific row in question ?
>> > 2. The full row in question ?
>> > 3. The full CF ?
>> >
>> > I doubt read does any locks.
>> >
>> > Thanks.
>> >
>>
>>
>>
>> --
>> Jonathan Ellis
>> Project Chair, Apache Cassandra
>> co-founder of DataStax, the source for professional Cassandra support
>> http://www.datastax.com
>>
>
>
>
> --
> It's always darkest just before you are eaten by a grue.

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