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From "Chao Shi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CRUNCH-351) Improve performance of Shard#shard on large records
Date Mon, 24 Feb 2014 13:47:20 GMT

    [ https://issues.apache.org/jira/browse/CRUNCH-351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13910306#comment-13910306
] 

Chao Shi commented on CRUNCH-351:
---------------------------------

bq. with the idea of having a really small number of different keys so that sorting the keys
within each partition would require almost no processing.

I think I have missed something here. I guess there must be some optimization in MR for such
case. Could you explain more how this works?

bq. count = (++count % (numPartitions * 3));

Is it identical to "count = ++count % numPartitions", given the partition function is "key
% numPartitions"?

> Improve performance of Shard#shard on large records
> ---------------------------------------------------
>
>                 Key: CRUNCH-351
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-351
>             Project: Crunch
>          Issue Type: Improvement
>            Reporter: Chao Shi
>            Assignee: Chao Shi
>         Attachments: crunch-351-v2.patch, crunch-351.patch
>
>
>     This avoids sorting on the input data, which may be long and make
>     shuffle phase slow. The improvement is to sort on pseudo-random numbers.



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