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From james anderson <james.ander...@setf.de>
Subject Re: batch_mutate atomicity
Date Sat, 07 Aug 2010 17:04:57 GMT
good afternoon;

On 2010-08-07, at 15:26 , Jonathan Ellis wrote:

> 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.

yes, those terms are not new.

it remains, that the answer with respect to isolation would be  
clearer were it expressed in terms of cassandra's operations. given  
the two-level map passed to batch_mutate,

is it that another thread could see the effect of some mutation  
object in one entry of the inner key map, but not see the effect of  
some other mutation object in the same entry of the inner key map?

or

is it that another thread could see the effect of one set of mutation  
objects in one entry of the inner key map, but not see the effect of  
some other set of mutation object in a different entry of the inner  
key map?

which one?

>
> On Sat, Aug 7, 2010 at 12:50 AM, james anderson  
> <james.anderson@setf.de> wrote:
>> good morning;
>>
>> On 2010-08-07, at 02:45 , Jonathan Ellis wrote:
>>
>>> Everything in the same key of a batch_mutate is atomic.  (But not
>>> isolated.)
>>>
>>
>> what does the distinction mean in the context of cassandra?
>> is it that the execution of an operation with the same key could  
>> see the
>> effect of the 'first' mutation on one column family but not  
>> another, or that
>> they could see the presence/absence of some columns in a row, but not
>> others, or?
>>
>> would it be possible to illustrate the difference with some simple  
>> examples.
>>
>>> On Fri, Aug 6, 2010 at 2:15 PM, B. Todd Burruss  
>>> <bburruss@real.com> wrote:
>>>>
>>>> ok i just saw the FAQ
>>>> (http://wiki.apache.org/cassandra/FAQ#batch_mutate_atomic)
>>>>
>>>> follow up question ...
>>>>
>>>> it states that "As a special case, mutations against a single  
>>>> key are
>>>> atomic, but more generally no" ... i interpret that to also mean  
>>>> " ..
>>>> mutations against a single key in the same CF ... "
>>>>
>>>> so if i have several mutatations against a single key, but multiple
>>>> column families i assume this is not atomic?
>>>>
>>>> thx
>>>>
>>>>
>>>> On Fri, 2010-08-06 at 11:08 -0700, Todd Burruss wrote:
>>>>>
>>>>> if i am using batch_mutate to update/insert two columns in the  
>>>>> same CF
>>>>> and same key, is this an atomic operation?
>>>>>
>>>>> i understand that an operation on a single key in a CF is  
>>>>> atomic, but
>>>>> not sure if the above scenario boils down to two operations or
>>>>> considered one operation.
>>>>>
>>>>> thx
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> Jonathan Ellis
>>> Project Chair, Apache Cassandra
>>> co-founder of Riptano, the source for professional Cassandra support
>>> http://riptano.com
>>
>>
>
>
>
> -- 
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support
> http://riptano.com


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