Hi Tupshin,
Thanks for your help! Unfortunately in my case, I will need to do a
compare and set in which the compare is against a value in a dynamic column.
In general, I need to be able to do the following:
 Check whether a given value exists in a dynamic column
 If so, perform some number of insertions / deletions for dynamic
columns in the same row (i.e., with the same partition key as the dynamic
column used for the compare)
I think you are correct that I need
https://issues.apache.org/jira/browse/CASSANDRA5633 to be implemented. Is
there any way to vote for that to get picked up again? :)
Best regards,
Clint
On Mon, Feb 24, 2014 at 2:32 PM, Tupshin Harper <tupshin@tupshin.com> wrote:
> Hi Clint,
>
> That does appear to be an omission in CQL3. It would be possible to
> simulate it by doing
> BEGIN BATCH
> UPDATE foo SET z = 10 WHERE x = 'a' AND y = 1 IF t= 2 AND z=10;
> UPDATE foo SET t = 5,z=6 where x = 'a' AND y = 4
> APPLY BATCH;
>
> However, this does a redundant write to the first row if the condition
> holds, and I certainly wouldn't recommend doing that routinely.
>
> Alternatively, depending on your needs, you might be able to use a static
> column (coming with 2.0.6) as your conditional flag, as that column is
> shared by all rows in the partition.
>
> Tupshin
>
>
>
> On Mon, Feb 24, 2014 at 3:57 PM, Clint Kelly <clint.kelly@gmail.com>wrote:
>
>> Hi Tupshin,
>>
>> Thanks for your help; I appreciate it.
>>
>> Could I do something like the following?
>>
>> Given the same table you started with:
>>
>> x  y  t  z
>> +++
>> a  1  2  10
>> a  2  2  20
>>
>> I'd like to write a compareandset that does something like:
>>
>> "If there is a row with (x,y,t,z) = (a,1,2,10), then update/insert a
>> row with (x,y,t,z) = (a,3,4,5) and update/insert a row with (x,y,t,z)
>> = (a,4,5,6)."
>>
>>
>> I don't see how I could do this with what you outlined abovejust
>> curious. It seems like what I describe above under the hood would be
>> a compareand(batch)set on a single wide row, so it maybe is
>> possible with the Thrift API (I have to check).
>>
>> Thanks again!
>>
>> Best regards,
>> Clint
>>
>> On Sat, Feb 22, 2014 at 11:38 AM, Tupshin Harper <tupshin@tupshin.com>
>> wrote:
>> > #5633 was actually closed because the static columns feature
>> > (https://issues.apache.org/jira/browse/CASSANDRA6561) which has been
>> > checked in to the 2.0 branch but is not yet part of a release (it will
>> be in
>> > 2.0.6).
>> >
>> > That feature will let you update multiple rows within a single
>> partition by
>> > doing a CAS write based on a static column shared by all rows within the
>> > partition.
>> >
>> > Example extracted from the ticket:
>> > CREATE TABLE foo (
>> > x text,
>> > y bigint,
>> > t bigint static,
>> > z bigint,
>> > PRIMARY KEY (x, y) );
>> >
>> > insert into foo (x,y,t, z) values ('a', 1, 1, 10);
>> > insert into foo (x,y,t, z) values ('a', 2, 2, 20);
>> >
>> > select * from foo;
>> >
>> > x  y  t  z
>> > +++
>> > a  1  2  10
>> > a  2  2  20
>> > (Note that both values of "t" are 2 because it is static)
>> >
>> >
>> > begin batch update foo set z = 1 where x = 'a' and y = 1; update foo
>> set z
>> > = 2 where x = 'a' and y = 2 if t = 4; apply batch;
>> >
>> > [applied]  x  y  t
>> > +++
>> > False  a  null  2
>> >
>> > (Both updates failed to apply because there was an unmet conditional on
>> one
>> > of them)
>> >
>> > select * from foo;
>> >
>> > x  y  t  z
>> > +++
>> > a  1  2  10
>> > a  2  2  20
>> >
>> >
>> > begin batch update foo set z = 1 where x = 'a' and y = 1; update foo
>> set z =
>> > 2 where x = 'a' and y = 2 if t = 2; apply batch;
>> >
>> > [applied]
>> > 
>> > True
>> >
>> > (both updates succeeded because the check on t succeeded)
>> >
>> > select * from foo;
>> > x  y  t  z
>> > +++
>> > a  1  2  1
>> > a  2  2  2
>> >
>> > Hope this helps.
>> >
>> > Tupshin
>> >
>> >
>> >
>> > On Fri, Feb 21, 2014 at 6:05 PM, DuyHai Doan <doanduyhai@gmail.com>
>> wrote:
>> >>
>> >> Hello Clint
>> >>
>> >> The Resolution status of the JIRA is set to "Later", probably the
>> >> implementation is not done yet. The JIRA was opened to discuss about
>> impl
>> >> strategy but nothing has been coded so far I guess.
>> >>
>> >>
>> >>
>> >> On Sat, Feb 22, 2014 at 12:02 AM, Clint Kelly <clint.kelly@gmail.com>
>> >> wrote:
>> >>>
>> >>> Folks,
>> >>>
>> >>> Does anyone know how I can modify multiple rows at once in a
>> >>> lightweight transaction in CQL3?
>> >>>
>> >>> I saw the following ticket:
>> >>>
>> >>> https://issues.apache.org/jira/browse/CASSANDRA5633
>> >>>
>> >>> but it was not obvious to me from the comments how (or whether) this
>> >>> got resolved. I also couldn't find anything in the DataStax
>> >>> documentation about how to perform these operations.
>> >>>
>> >>> I'm in particular interested in how to perform a compareandset
>> >>> operation that modifies multiple rows (with the same partition key)
>> >>> using the DataStax Java driver.
>> >>>
>> >>> Thanks!
>> >>>
>> >>> Best regards,
>> >>> Clint
>> >>
>> >>
>> >
>>
>
>
