Incorect Input to Reduce

Jonathan Langevin jlangevin at loomlearning.com
Wed Nov 30 10:11:03 EST 2011


Excellent tip Sean, works great for a similar issue I was having.
If I already had args being passed to my reduce phase though (such as when
calling Riak.reduceSlice), is it possible to specify only_1 and still
ensure that my regular args pass through to the function as expected? For
instance, reduceSlice expects [int,int], which conflicts with
{"somearg":blah}.
My thought is to now encapsulate my original function call, but I want to
make sure I'm not missing something in Riak that already handles this issue.

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* Jonathan Langevin
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On Wed, Nov 30, 2011 at 10:01 AM, Sean Cribbs <sean at basho.com> wrote:

> Hi Yehuda,
>
> Your reduce function is not guaranteed to run across all inputs in the
> first application, but may be applied many times as new inputs come in.
> Riak will batch up reduce inputs until a certain number or timeout is
> reached, then apply the function and take its output to be part of the
> inputs for the next application. If it is absolutely necessary to run the
> reduce function only once, use "reduce_phase_only_1" as the "arg" (only
> works on Riak 1.0.x, example in Ruby):
>
> mr.reduce("function(v){...}", :arg => {:reduce_phase_only_1 => true},
> :keep => true)
>
> Hope that helps!
>
> On Wed, Nov 30, 2011 at 9:03 AM, Yehuda Zargrov <Yehuda at conduit.com>wrote:
>
>> Hi,****
>>
>> ** **
>>
>> I’ve posted a mail on this few days ago, but went a bit further since
>> then.****
>>
>> ** **
>>
>> I’m using ripple, running a map function on some input and getting a list
>> of about 50 items.****
>>
>> ** **
>>
>> Right after that, I’m running a reduce function. The first thing I do in
>> it is putting the length of v (the input) as an item in a list.****
>>
>> ** **
>>
>> When printing the result I see that the length is 13.****
>>
>> ** **
>>
>> It’s like something has happened between the map and reduce phases.****
>>
>> ** **
>>
>> Any ideas?****
>>
>> ** **
>>
>>   ****
>>
>> [image: Description:
>> C:\Users\Yehuda\AppData\Roaming\Microsoft\Signatures\logo.gif]****
>>
>> *Yehuda Zargrov**
>> *Software Engineer****
>>
>> *Conduit Your Site* <http://www.conduit.com/>****
>>
>> *t:* 972.8.9461713 ext +314 |   *m:* +972503473119   |   *f:*
>> +97286382140 ****
>>
>>
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>
>
> --
> Sean Cribbs <sean at basho.com>
> Developer Advocate
> Basho Technologies, Inc.
> http://www.basho.com/
>
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